Transmitting device, transmitting method, and communication system

ABSTRACT

A transmitting device of the present disclosure includes: a voltage generator that generates a predetermined voltage; a first driver including a first sub-driver and a second sub-driver, the first dub-driver that includes a first switch provided on a path from a first power source to a first output terminal, a second switch provided on a path from a second power source to the first output terminal, and a third switch provided on a path from the voltage generator to the first output terminal, and is allowed to set a voltage state of the first output terminal to any of a predetermined number of voltage states which are three or more voltage states, and the second sub-driver that is allowed to adjust a voltage in each of the voltage states of the first output terminal; and a controller that controls an operation of the first driver to perform emphasis.

TECHNICAL FIELD

The present disclosure relates to a transmitting device that transmits asignal, a transmitting method employed in such a transmitting device,and a communication system including such a transmitting device.

BACKGROUND ART

With high functionalization and multi-functionalization of electronicapparatuses in recent years, electronic apparatuses are equipped withvarious devices such as a semiconductor chip, a sensor, and a displaydevice. These devices exchange a lot of data between them, and an amountof data has increased with the high functionalization andmulti-functionalization of electronic apparatuses. Accordingly, ahigh-speed interface that is able to transmit and receive data, forexample, at several Gbps is often used to perform data exchange.

To improve communication performance of a high-speed interface, varioustechnologies are disclosed. For example, PTLs 1 and 2 disclose acommunication system that uses three transmission lines to transmitthree differential signals. Furthermore, for example, PTL 3 discloses acommunication system that performs pre-emphasis.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. H06-261092

PTL 2: U.S. Pat. No. 8,064,535

PTL 3: Japanese Unexamined Patent Application Publication No.2011-142382

SUMMARY OF THE INVENTION

Incidentally, reduction of power consumption is generally desired ofelectronic apparatuses, and reduction of power consumption is expectedof communication systems as well.

It is desirable to provide a transmitting device, a transmitting method,and a communication system that make it possible to reduce powerconsumption.

A first transmitting device according to an embodiment of the presentdisclosure includes a voltage generator, a first driver, and acontroller. The voltage generator generates a predetermined voltage. Thefirst driver includes a first sub-driver and a second sub-driver. Thefirst sub-driver includes a first switch provided on a path from a firstpower source to a first output terminal, a second switch provided on apath from a second power source to the first output terminal, and athird switch provided on a path from the voltage generator to the firstoutput terminal, and is allowed to set a voltage state of the firstoutput terminal to any of a predetermined number of voltage states whichare three or more voltage states. The second sub-driver is allowed toadjust a voltage in each of the voltage states of the first outputterminal. The controller controls an operation of the first driver toperform emphasis.

A second transmitting device according to an embodiment of the presentdisclosure includes a driver unit, a controller, and a voltagegenerator. The driver unit transmits a data signal with use of apredetermined number of voltage states which are three or more voltagestates, and is allowed to set a voltage in each of the voltage states.The controller sets an emphasis voltage in accordance with a transitionbetween the predetermined number of voltage states, thereby causing thedriver unit to perform emphasis. The driver unit includes a first switchprovided on a path from a first power source to an output terminal, asecond switch provided on a path from a second power source to theoutput terminal, and a third switch provided on a path from the voltagegenerator to the output terminal.

A transmitting method according to an embodiment of the presentdisclosure includes: controlling an operation of a first sub-driverincluding a first switch provided on a path from a first power source toa first output terminal, a second switch provided on a path from asecond power source to the first output terminal, and a third switchprovided on a path from a voltage generator to the first outputterminal, thereby setting a voltage state of the first output terminalto any of a predetermined number of voltage states which are three ormore voltage states; and controlling an operation of a secondsub-driver, thereby adjusting a voltage in each of the voltage states ofthe first output terminal to perform emphasis.

A communication system according to an embodiment of the presentdisclosure includes a transmitting device and a receiving device. Thetransmitting device includes a voltage generator, a first driver, and acontroller. The voltage generator generates a predetermined voltage. Thefirst driver includes a first sub-driver and a second sub-driver. Thefirst sub-driver includes a first switch provided on a path from a firstpower source to a first output terminal, a second switch provided on apath from a second power source to the first output terminal, and athird switch provided on a path from the voltage generator to the firstoutput terminal, and is allowed to set a voltage state of the firstoutput terminal to any of a predetermined number of voltage states whichare three or more voltage states. The second sub-driver is allowed toadjust a voltage in each of the voltage states of the first outputterminal. The controller controls an operation of the first driver toperform emphasis.

In the first transmitting device, the transmitting method, and thecommunication system according to the embodiments of the presentdisclosure, the voltage state of the first output terminal is set to anyof the predetermined number of voltage states, which are three or morevoltage states, by the first sub-driver. Furthermore, the voltage ineach of the voltage states of the first output terminal is adjusted bythe second sub-driver. The first sub-driver and the second sub-driverare controlled to perform emphasis. The first sub-driver is providedwith the first switch on the path from the first power source to thefirst output terminal, the second switch on the path from the secondpower source to the first output terminal, and the third switch on thepath from the voltage generator to the first output terminal.

In the second transmitting device according to the embodiment of thepresent disclosure, the data signal is transmitted with use of thepredetermined number of voltage states which are three or more voltagestates. Then, emphasis is performed through setting the emphasis voltagein accordance with a transition between the predetermined number ofvoltage states. The driver unit is provided with the first switch on thepath from the first power source to the first output terminal, thesecond switch on the path from the second power source to the firstoutput terminal, and the third switch on the path from the voltagegenerator to the first output terminal.

According to the first and second transmitting devices, the transmittingmethod, and the communication system of the embodiments of the presentdisclosure, the first switch is provided on the path from the firstpower source to the first output terminal; the second switch is providedon the path from the second power source to the first output terminal;and the third switch is provided on the path from the voltage generatorto the first output terminal. This makes it possible to reduce powerconsumption. It is to be noted that the effects described here are notnecessarily limited, and any effect described in the present disclosuremay be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of acommunication system according to an embodiment of the presentdisclosure.

FIG. 2 is a diagram that describes a voltage state of a signal that thecommunication system illustrated in FIG. 1 transmits and receives.

FIG. 3 is another diagram that describes the voltage state of the signalthat the communication system illustrated in FIG. 1 transmits andreceives.

FIG. 4 is a diagram that describes transition of symbols that thecommunication system illustrated in FIG. 1 transmits and receives.

FIG. 5 is a block diagram illustrating a configuration example of atransmitter illustrated in FIG. 1.

FIG. 6 is a table illustrating an operation example of a transmittingsymbol generator illustrated in FIG. 5.

FIG. 7 is a block diagram illustrating a configuration example of anoutput unit illustrated in FIG. 5.

FIG. 8 is a block diagram illustrating a configuration example of adriver illustrated in FIG. 7.

FIG. 9 is a table illustrating an operation example of an emphasiscontroller illustrated in FIG. 7.

FIG. 10A is a diagram that describes an operation example of the driverillustrated in FIG. 8.

FIG. 10B is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 10C is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 11A is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 11B is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 11C is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 12A is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 12B is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 12C is a diagram that describes another operation example of thedriver illustrated in FIG. 8.

FIG. 13 is a block diagram illustrating a configuration example of areceiver illustrated in FIG. 1.

FIG. 14 is a diagram that describes an example of a receiving operationof the receiver illustrated in FIG. 13.

FIG. 15 is a waveform diagram illustrating an operation example of thetransmitter illustrated in FIG. 7.

FIG. 16 is a schematic diagram illustrating an operation example of thedriver illustrated in FIG. 8.

FIG. 17 is a waveform diagram illustrating another operation example ofthe transmitter illustrated in FIG. 7.

FIG. 18 is a schematic diagram illustrating another operation example ofthe driver illustrated in FIG. 8.

FIG. 19 is a waveform diagram illustrating another operation example ofthe transmitter illustrated in FIG. 7.

FIG. 20 is a schematic diagram illustrating an operation example of thedriver illustrated in FIG. 8.

FIG. 21A is a timing waveform diagram illustrating an operation exampleof the communication system illustrated in FIG. 1.

FIG. 21B is a timing waveform diagram illustrating another operationexample of the communication system illustrated in FIG. 1.

FIG. 21C is a timing waveform diagram illustrating another operationexample of the communication system illustrated in FIG. 1.

FIG. 21D is a timing waveform diagram illustrating another operationexample of the communication system illustrated in FIG. 1.

FIG. 21E is a timing waveform diagram illustrating another operationexample of the communication system illustrated in FIG. 1.

FIG. 22 is an eye diagram illustrating an example of signals in a casewhere a de-emphasis operation is performed.

FIG. 23 is an eye diagram illustrating an example of the signals in acase where the de-emphasis operation is not performed.

FIG. 24 is a block diagram illustrating a configuration example of anoutput unit according to a comparative example.

FIG. 25 is a block diagram illustrating a configuration example of adriver illustrated in FIG. 24.

FIG. 26A is a diagram that describes an operation example of the driverillustrated in FIG. 25.

FIG. 26B is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 26C is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 27A is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 27B is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 27C is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 28A is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 28B is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 28C is a diagram that describes another operation example of thedriver illustrated in FIG. 25.

FIG. 29 is a block diagram illustrating a configuration example of adriver according to a modification example.

FIG. 30 is a block diagram illustrating a configuration example of adriver according to another modification example.

FIG. 31 is a block diagram illustrating a configuration example of adriver according to another modification example.

FIG. 32 is a block diagram illustrating a configuration example of atransmitter according to a modification example.

FIG. 33 is a block diagram illustrating a configuration example of anoutput unit illustrated in FIG. 32.

FIG. 34 is a diagram that describes a voltage state of a signal that acommunication system according to another modification example transmitsand receives.

FIG. 35 is a perspective view of an appearance configuration of asmartphone to which the communication system according to the embodimentis applied.

FIG. 36 is a block diagram illustrating a configuration example of anapplication processor to which the communication system according to theembodiment is applied.

FIG. 37 is a block diagram illustrating a configuration example of animage sensor to which the communication system according to theembodiment is applied.

FIG. 38 is a block diagram depicting an example of schematicconfiguration of a vehicle control system.

FIG. 39 is a diagram of assistance in explaining an example ofinstallation positions of an outside-vehicle information detectingsection and an imaging section.

FIG. 40 is a view depicting an example of a schematic configuration ofan endoscopic surgery system.

FIG. 41 is a block diagram depicting an example of a functionalconfiguration of a camera head and a camera control unit (CCU) depictedin FIG. 40.

MODES FOR CARRYING OUT THE INVENTION

In the following, some embodiments of the present disclosure will bedescribed in detail with reference to drawings. It is to be noted thatdescription is made in the following order.

1. Embodiment 2. Application Example 1. Embodiment Configuration Example

FIG. 1 illustrates a configuration example of a communication system (acommunication system 1) according to an embodiment. The communicationsystem 1 performs de-emphasis to improve communication performance.

The communication system 1 includes a transmitting device 10, atransmission line 100, and a receiving device 30. The transmittingdevice 10 has three output terminals ToutA, ToutB, and ToutC. Thetransmission line 100 includes lines 110A, 110B, and 110C. The receivingdevice 30 has three input terminals TinA, TinB, and TinC. The outputterminal ToutA of the transmitting device 10 and the input terminal TinAof the receiving device 30 are coupled to each other through the line110A; the output terminal ToutB of the transmitting device 10 and theinput terminal TinB of the receiving device 30 are coupled to each otherthrough the line 110B; the output terminal ToutC of the transmittingdevice 10 and the input terminal TinC of the receiving device 30 arecoupled to each other through the line 110C. Characteristic impedancesof the lines 110A to 110C are about 50[Ω] in this example.

The transmitting device 10 outputs signals SIGA, SIGB, and SIGC from theoutput terminals ToutA, ToutB, and ToutC, respectively. Then, thereceiving device 30 receives the signals SIGA, SIGB, and SIGC throughthe input terminals TinA, TinB, and TinC, respectively. The signalsSIGA, SIGB, and SIGC each possibly take three voltage states SH, SM, andSL.

FIG. 2 illustrates the three voltage states SH, SM, and SL. The voltagestate SH is a state corresponding to three high-level voltages VH (VH0,VH1, and VH2). Of the high-level voltages VH0, VH1, and VH2, thehigh-level voltage VH0 is the lowest voltage, and the high-level voltageVH2 is the highest voltage. The voltage state SM is a statecorresponding to three medium-level voltages VM (VM0, VM1plus, andVM1minus). Of the medium-level voltages VM0, VM1plus, and VM1minus, themedium-level voltage VM1minus is the lowest voltage, and themedium-level voltage VM1plus is the highest voltage. The voltage stateSL is a state corresponding to three low-level voltages VL (VL0, VL1,and VL2). Of the low-level voltages VL0, VL1, and VL2, the low-levelvoltage VL0 is the highest voltage, and the low-level voltage VL2 is thelowest voltage. The high-level voltage VH2 is a high-level voltage in acase where de-emphasis is not applied; the medium-level voltage VM0 is amedium-level voltage in a case where de-emphasis is not applied; thelow-level voltage VL2 is a low-level voltage in a case where de-emphasisis not applied.

FIG. 3 illustrates voltage states of signals SIGA, SIGB, and SIGC. Thetransmitting device 10 transmits six symbols “+x”, “−x”, “+y”, “−y”,“+z”, and “−z” with use of three signals SIGA, SIGB, and SIGC. Forexample, in a case where the symbol “+x” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SH, thesignal SIGB to the voltage state SL, and the signal SIGC to the voltagestate SM. In a case where the symbol “−x” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SL, thesignal SIGB to the voltage state SH, and the signal SIGC to the voltagestate SM. In a case where the symbol “+y” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SM, thesignal SIGB to the voltage state SH, and the signal SIGC to the voltagestate SL. In a case where the symbol “−y” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SM, thesignal SIGB to the voltage state SL, and the signal SIGC to the voltagestate SH. In a case where the symbol “+z” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SL, thesignal SIGB to the voltage state SM, and the signal SIGC to the voltagestate SH. In a case where the symbol “−z” is transmitted, thetransmitting device 10 sets the signal SIGA to the voltage state SH, thesignal SIGB to the voltage state SM, and the signal SIGC to the voltagestate SL.

The transmission line 100 transmits a sequence of symbols with use ofsuch signals SIGA, SIGB, and SIGC. That is, the three lines 110A, 110B,and 110C serve as one lane that transmits a sequence of symbols.

(Transmitting Device 10)

As illustrated in FIG. 1, the transmitting device 10 includes a clockgenerator 11, a processor 12, and a transmitter 20.

The clock generator 11 generates a clock signal TxCK. A frequency of theclock signal TxCK is, for example, 2.5 [GHz]. It is to be noted that thefrequency is not limited thereto, and for example, in a case where acircuit in the transmitting device 10 is configured with use of aso-called half-rate architecture, it is possible to set the frequency ofthe clock signal TxCK to 1.25 [GHz]. The clock generator 11 includes,for example, a PLL (phase-locked loop), and generates a clock signalTxCK, for example, on the basis of a reference clock (not illustrated)supplied from outside of the transmitting device 10. Then, the clockgenerator 11 supplies this clock signal TxCK to the processor 12 and thetransmitter 20.

The processor 12 performs a predetermined process, thereby generatingtransition signals TxF0 to TxF6, TxR0 to TxR6, and TxP0 to TxP6. A setof the transition signals TxF0, TxR0, and TxP0 here indicates a symboltransition in a sequence of symbols that the transmitting device 10transmits. Likewise, a set of the transition signals TxF1, TxR1, andTxP1, a set of the transition signals TxF2, TxR2, and TxP2, a set of thetransition signals TxF3, TxR3, and TxP3, a set of the transition signalsTxF4, TxR4, and TxP4, a set of the transition signals TxF5, TxR5, andTxP5, and a set of the transition signals TxF6, TxR6, and TxP6 eachindicate a symbol transition. That is, the processor 12 generates sevensets of transition signals. Hereinafter, transition signals TxF, TxR,and TxP are used to represent any set of the seven sets of transitionsignals appropriately.

FIG. 4 illustrates a relationship between transition signals TxF, TxR,and TxP and a symbol transition. Numeral values of three digits assignedto each transition denote respective values of signals TxF, TxR, and TxPin this order.

The transition signal TxF (Flip) causes a symbol transition between “+x”and “−x”, a symbol transition between “+y” and “−y”, and a symboltransition between “+z” and “−z”. Specifically, in a case where thetransition signal TxF is “1”, a symbol makes a transition so as tochange its polarity (for example, from “+x” to “−x”); in a case wherethe transition signal TxF is “0”, a symbol does not make such atransition.

The transition signals TxR(Rotation) and TxP(Polarity) cause a symboltransition between symbols other than between “+x” and “−x”, between“+y” and “−y”, and between “+z” and “−z” in a case where the transitionsignal TxF is “0”. Specifically, in a case where the transition signalsTxR and TxP are “1” and “0”, respectively, a symbol makes a transitionin a clockwise direction in FIG. 4 while maintaining its polarity (forexample, from “+x” to “+y”); in a case where the transition signals TxRand TxP are “1” and “1”, respectively, a symbol changes its polarity andmakes a transition in the clockwise direction in FIG. 4 (for example,from “+x” to “−y”). Furthermore, in a case where the transition signalsTxR and TxP are “0” and “0”, respectively, a symbol makes a transitionin a counterclockwise direction in FIG. 4 while maintaining its polarity(for example, from “+x” to “+z”); in a case where the transition signalsTxR and TxP are “0” and “1”, respectively, a symbol changes its polarityand makes a transition in the counterclockwise direction in FIG. 4 (forexample, from “+x” to “−z”).

The processor 12 generates seven sets of such transition signals TxF,TxR, and TxP. Then, the processor 12 supplies these seven sets oftransition signals TxF, TxR, and TxP (transition signals TxF0 to TxF6,TxR0 to TxR6, and TxP0 to TxP6) to the transmitter 20.

The transmitter 20 generates signals SIGA, SIGB, and SIGC on the basisof the transition signals TxF0 to TxF6, TxR0 to TxR6, and TxP0 to TxP6.

FIG. 5 illustrates a configuration example of the transmitter 20. Thetransmitter 20 includes serializers 21F, 21R, and 21P, a transmittingsymbol generator 22, and an output unit 26.

The serializer 21F serializes transition signals TxF0 to TxF6 in thisorder on the basis of the transition signals TxF0 to TxF6 and a clocksignal TxCK, thereby generating a transition signal TxF9. The serializer21R serializes transition signals TxR0 to TxR6 in this order on thebasis of the transition signals TxR0 to TxR6 and the clock signal TxCK,thereby generating a transition signal TxR9. The serializer 21Pserializes transition signals TxP0 to TxP6 in this order on the basis ofthe transition signals TxP0 to TxP6 and the clock signal TxCK, therebygenerating a transition signal TxP9.

The transmitting symbol generator 22 generates symbol signals Tx1, Tx2,and Tx3 and symbol signals Dtx1, Dtx2, and Dtx3 on the basis of thetransition signals TxF9, TxR9, and TxP9 and the clock signal TxCK. Thetransmitting symbol generator 22 includes a signal generator 23 and aflip-flop 24.

The signal generator 23 generates symbol signals Tx1, Tx2, and Tx3related to a current symbol NS on the basis of the transition signalsTxF9, TxR9, and TxP9 and the symbol signals Dtx1, Dtx2, and Dtx3.Specifically, on the basis of a symbol (a previous symbol DS) indicatedby the symbol signals Dtx1, Dtx2, and Dtx3 and the transition signalsTxF9, TxR9, and TxP9, the signal generator 23 finds the current symbolNS as illustrated in FIG. 4, and outputs the current symbol NS as thesymbol signals Tx1, Tx2, and Tx3.

The flip-flop 24 samples the symbol signals Tx1, Tx2, and Tx3 on thebasis of the clock signal TxCK, and outputs a result of the sampling asthe symbol signals Dtx1, Dtx2, and Dtx3.

FIG. 6 illustrates an operation example of the transmitting symbolgenerator 22. This FIG. 6 illustrates a symbol NS generated on the basisof the symbol DS indicated by the symbol signals Dtx1, Dtx2, and Dtx3and the transition signals TxF9, TxR9, and TxP9. A case where the symbolDS is “+x” is described as an example. In a case where the transitionsignals TxF9, TxR9, and TxP9 are “000”, the symbol NS is “+z”; in a casewhere the transition signals TxF9, TxR9, and TxP9 are “001”, the symbolNS is “−z”; in a case where the transition signals TxF9, TxR9, and TxP9are “010”, the symbol NS is “+y”; in a case where the transition signalsTxF9, TxR9, and TxP9 are “011”, the symbol NS is “−y”; in a case wherethe transition signals TxF9, TxR9, and TxP9 is “1XX”, the symbol NS is“−x”. Here, “X” indicates that it makes no difference whether X is “1”or “0”. The same applies to a case where the symbol DS is any of “−x”,“+y”, “−y”, “+z”, and “−z”.

The output unit 26 generates the signals SIGA, SIGB, and SIGC on thebasis of the symbol signals Tx1, Tx2, and Tx3, the symbol signals Dtx1,Dtx2, and Dtx3, and the clock signal TxCK.

FIG. 7 illustrates a configuration example of the output unit 26. Theoutput unit 26 includes a voltage generator 50, driver controllers 27Nand 27D, emphasis controllers 28A, 28B, and 28C, and drivers 29A, 29B,and 29C.

The voltage generator 50 generates a voltage Vdc corresponding to themedium-level voltage VM0. The voltage generator 50 includes a referencevoltage generator 51, an operational amplifier 52, and a capacitor 53.The reference voltage generator 51 includes, for example, a bandgapreference circuit, and generates a reference voltage Vref correspondingto the medium-level voltage VM0. A positive input terminal of theoperational amplifier 52 is supplied with the reference voltage Vref,and a negative input terminal is coupled to an output terminal. Thisconfiguration makes the operational amplifier 52 operate as a voltagefollower and output the voltage Vdc corresponding to the medium-levelvoltage VM0. One end of the capacitor 53 is coupled to the outputterminal of the operational amplifier 52, and the other end is grounded.

The driver controller 27N generates signals MAINAN and SUBAN, signalsMAINBN and SUBBN, and signals MAINCN and SUBCN on the basis of thesymbol signals Tx1, Tx2, and Tx3 related to the current symbol NS andthe clock signal TxCK. Specifically, on the basis of the current symbolNS indicated by symbol signals Tx1, Tx2, and Tx3, the driver controller27N finds respective voltage states of signals SIGA, SIGB, and SIGC asillustrated in FIG. 3. Then, for example, in a case where the signalSIGA is put into the voltage state SH, the driver controller 27N setsthe signals MAINAN and SUBAN to “1” and “0”, respectively; in a casewhere the signal SIGA is put into the voltage state SL, the drivercontroller 27N sets the signals MAINAN and SUBAN to “0” and “1”,respectively; and in a case where the signal SIGA is put into thevoltage state SM, the driver controller 27N sets the signals MAINAN andSUBAN to both “1” or both “0”. The same applies to the signals MAINBNand SUBBN and the signals MAINCN and SUBCN. Then, the driver controller27N supplies the signals MAINAN and SUBAN to the emphasis controller28A, the signals MAINBN and SUBBN to the emphasis controller 28B, andthe signals MAINCN and SUBCN to the emphasis controller 28C.

The driver controller 27D generates signals MAINAD and SUBAD, signalsMAINBD and SUBBD, and signals MAINCD and SUBCD on the basis of thesymbol signals Dtx1, Dtx2, and Dtx3 related to the previous symbol DSand the clock signal TxCK. The driver controller 27D has the samecircuit configuration as the driver controller 27N. Then, the drivercontroller 27D supplies the signals MAINAD and SUBAD to the emphasiscontroller 28A, the signals MAINBD and SUBBD to the emphasis controller28B, and the signals MAINCD and SUBCD to the emphasis controller 28C.

The emphasis controller 28A generates six signals UPA0, UPA1, MDA0,MDA1, DNA0, and DNA1 on the basis of the signals MAINAN and SUBAN andthe signals MAINAD and SUBAD. The driver 29A generates the signal SIGAon the basis of the six signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1.

The emphasis controller 28B generates six signals UPB0, UPB1, MDB0,MDB1, DNB0, and DNB1 on the basis of the signals MAINBN and SUBBN andthe signals MAINBD and SUBBD. The driver 29B generates the signal SIGBon the basis of the six signals UPB0, UPB1, MDB0, MDB1, DNB0, and DNB1.

The emphasis controller 28C generates six signals UPC0, UPC1, MDC0,MDC1, DNC0, and DNC1 on the basis of the signals MAINCN and SUBCN andthe signals MAINCD and SUBCD. The driver 29C generates the signal SIGCon the basis of the six signals UPC0, UPC1, MDC0, MDC1, DNC0, and DNC1.

FIG. 8 illustrates a configuration example of the driver 29A. It is tobe noted that the same applies to the drivers 29B and 29C. The driver29A includes two sub-drivers 290 and 291. The sub-driver 290 includes Mcircuits U0 (circuits U0 ₁ to U0 _(M)), M circuits D0 (circuits D0 ₁ toD0 _(M)), and M circuits M0 (circuits M0 ₁ to M0 _(M)). The sub-driver291 includes N circuits U1 (circuits U1 ₁ to U1 _(N)), N circuits D1(circuits D1 ₁ to D1 _(N)), and N circuits M1 (circuits M1 ₁ to M1_(N)). In this example, “M” is a number greater than “N”. Furthermore,in this example, the number of the circuits U0, the number of thecircuits M0, the number of the circuits D0, the number of the circuitsU1, the number of the circuits M1, and the number of the circuits D1 areconfigured to be separately settable.

The circuits U0 ₁ to U0 _(M) and U1 ₁ to U1 _(N) each include atransistor 91 and a resistor 92. In this example, the transistor 91 isan N-channel MOS (Metal Oxide Semiconductor) type FET (Field EffectTransistor). In each of the circuits U0 ₁ to U0 _(M), a gate of thetransistor 91 is supplied with the signal UPA0, and a drain is suppliedwith a voltage V1, and a source is coupled to one end of the resistor92. In each of the circuits U1 ₁ to U1 _(N), the gate of the transistor91 is supplied with the signal UPA1, and the drain is supplied with thevoltage V1, and the source is coupled to the one end of the resistor 92.In each of the circuits U0 ₁ to U0 _(M) and U1 ₁ to U1 _(N), the one endof the resistor 92 is coupled to the source of the transistor 91, andthe other end is coupled to the output terminal ToutA. The sum of anon-state resistance value of the transistor 91 and a resistance value ofthe resistor 92 is “50×(M+N)”[Ω] in this example.

The circuits D0 ₁ to D0 _(M) and D1 ₁ to D1 _(N) each include a resistor93 and a transistor 94. In each of the circuits D0 ₁ to D0 _(M) and D1 ₁to D1 _(N), one end of the resistor 93 is coupled to the output terminalToutA, and the other end is coupled to a drain of the transistor 94. Inthis example, the transistor 94 is an N-channel MOS type FET. In each ofthe circuits D0 ₁ to D0 _(M), a gate of the transistor 94 is suppliedwith the signal DNA0, and the drain is coupled to the other end of theresistor 93, and a source is grounded. In each of the circuits D1 ₁ toD1 _(N), the gate of the transistor 94 is supplied with the signal DNA1,and the drain is coupled to the other end of the resistor 93, and thesource is grounded. The sum of a resistance value of the resistor 93 andan on-state resistance value of the transistor 94 is “50×(M+N)”[Ω] inthis example.

The circuits M0 ₁ to M0 _(M) and M1 ₁ to M1 _(N) each include atransistor 95 and a resistor 96. In this example, the transistor 95 isan N-channel MOS type FET. In each of the circuits M0 ₁ to M0 _(M), agate of the transistor 95 is supplied with the signal MDA0, and a sourceis supplied with the voltage Vdc generated by the voltage generator 50,and a drain is coupled to one end of the resistor 96. In each of thecircuits M1 ₁ to M1 _(N), the gate of the transistor 95 is supplied withthe signal MDA1, and the source is supplied with the voltage Vdcgenerated by the voltage generator 50, and the drain is coupled to oneend of the resistor 96. In each of the circuits M0 ₁ to M0 _(M) and M1 ₁to M1 _(N), one end of the resistor 96 is coupled to the drain of thetransistor 95, and the other end is coupled to the output terminalToutA. The sum of an on-state resistance value of the transistor 95 anda resistance value of the resistor 96 is “50×(M+N)”[Ω] in this example.

FIG. 9 illustrates an operation example of the emphasis controller 28A.FIGS. 10A to 10C schematically illustrate an operation example of thedriver 29A in a case where the signal SIGA is put into the voltage stateSH. FIGS. 11A to 11C schematically illustrate an operation example ofthe driver 29A in a case where the signal SIGA is put into the voltagestate SM. FIGS. 12A to 12C schematically illustrate an operation exampleof the driver 29A in a case where the signal SIGA is put into thevoltage state SL. In FIGS. 10A to 10C, 11A to 11C, and 12A to 12C, ofthe circuits U0 ₁ to U0 _(M) and U1 ₁ to U1 _(N), a shaded circuitindicates a circuit in which the transistor 91 is in an on state, and anunshaded circuit indicates a circuit in which the transistor 91 is in anoff state. Likewise, of the circuits D0 ₁ to D0 _(M) and D1 ₁ to D1_(N), a shaded circuit indicates a circuit in which the transistor 94 isin the on state, and an unshaded circuit indicates a circuit in whichthe transistor 94 is in the off state. Furthermore, of the circuits M0 ₁to M0 _(M) and M1 ₁ to M1 _(N), a shaded circuit indicates a circuit inwhich the transistor 95 is in the on state, and an unshaded circuitindicates a circuit in which the transistor 95 is in the off state. Itis to be noted that here, the emphasis controller 28A and the driver 29Aare described as an example; however, the same applies to the emphasiscontroller 28B and the driver 29B and to the emphasis controller 28C andthe driver 29C.

In a case where the signals MAINAN and SUBAN related to the currentsymbol NS are “1” and “0”, respectively, the emphasis controller 28Asets a voltage of the signal SIGA to any of the three high-levelvoltages VH0, VH1, and VH2 as illustrated in FIGS. 10A to 10C.

Specifically, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“1”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “1” and “0”, respectively, the emphasis controller28A sets signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “110000”.Accordingly, in the driver 29A, as illustrated in FIG. 10A, thetransistors 91 in the circuits U0 ₁ to U0 _(M) and U1 ₁ to U1 _(N) gointo the on state. As a result, the voltage of the signal SIGA becomesthe high-level voltage VH2, and an output terminating resistance (anoutput impedance) of the driver 29A becomes about 50[Ω].

Furthermore, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “1” and “0”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “100100”.Accordingly, in the driver 29A, as illustrated in FIG. 10B, thetransistors 91 in the circuits U0 ₁ to U0 _(M) go into the on state, andthe transistors 95 in the circuits M1 ₁ to M1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the high-levelvoltage VH1, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω]. The same applies to acase where the signals MAINAD and SUBAD related to the previous symbolDS are “1” and “1”, respectively, and the signals MAINAN and SUBANrelated to the current symbol NS are “1” and “0”, respectively.

Moreover, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “1” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “1” and “0”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “100001”.Accordingly, in the driver 29A, as illustrated in FIG. 10C, thetransistors 91 in the circuits U0 ₁ to U0 _(M) go into the on state, andthe transistors 94 in the circuits D1 ₁ to D1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the high-levelvoltage VH0, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω].

Furthermore, in a case where the signals MAINAN and SUBAN related to thecurrent symbol NS are both “0” or both “1”, the emphasis controller 28Asets the voltage of the signal SIGA to any of the three medium-levelvoltages VM0, VM1plus, and VM1minus as illustrated in FIGS. 11A to 11C.

Specifically, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“1”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “0”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “011000”.Accordingly, in the driver 29A, as illustrated in FIG. 11A, thetransistors 95 in the circuits M0 ₁ to M0 _(M) go into the on state, andthe transistors 91 in the circuits U1 ₁ to U1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the medium-levelvoltage VM1plus, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω]. The same applies to acase where the signals MAINAD and SUBAD related to the previous symbolDS are “0” and “1”, respectively, and the signals MAINAN and SUBANrelated to the current symbol NS are “1” and “1”, respectively.

Furthermore, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “0”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “001100”.Accordingly, in the driver 29A, as illustrated in FIG. 11B, thetransistors 95 in the circuits M0 ₁ to M0 _(M) and M1 ₁ to M1 _(N) gointo the on state. As a result, the voltage of the signal SIGA becomesthe medium-level voltage VM0, and the output terminating resistance (theoutput impedance) of the driver 29A becomes about 50[Ω]. The sameapplies to a case where the signals MAINAD and SUBAD related to theprevious symbol DS are “1” and “1”, respectively, and the signals MAINANand SUBAN related to the current symbol NS are “0” and “0”,respectively. Furthermore, the same applies to a case where the signalsMAINAD and SUBAD related to the previous symbol DS are “0” and “0”,respectively, and the signals MAINAN and SUBAN related to the currentsymbol NS are “1” and “1”, respectively. Moreover, the same applies to acase where the signals MAINAD and SUBAD related to the previous symbolDS are “1” and “1”, respectively, and the signals MAINAN and SUBANrelated to the current symbol NS are “1” and “1”, respectively.

Moreover, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “1” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “0”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “001001”.Accordingly, in the driver 29A, as illustrated in FIG. 11C, thetransistors 95 in the circuits M0 ₁ to M0 _(M) go into the on state, andthe transistors 94 in the circuits D1 ₁ to D1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the medium-levelvoltage VM1minus, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω]. The same applies to acase where the signals MAINAD and SUBAD related to the previous symbolDS are “1” and “0”, respectively, and the signals MAINAN and SUBANrelated to the current symbol NS are “1” and “1”, respectively.

Furthermore, in a case where the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “1”, respectively, the emphasis controller28A sets the voltage of the signal SIGA to any of the low-level voltagesVL0, VL1, and VL2 as illustrated in FIGS. 12A to 12C.

Specifically, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“1”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “1”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “010010”.Accordingly, in the driver 29A, as illustrated in FIG. 12A, thetransistors 94 in the circuits D0 ₁ to D0 _(M) go into the on state, andthe transistors 91 in the circuits U1 ₁ to U1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the low-levelvoltage VL0, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω].

Furthermore, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “0” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “1”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “000110”.Accordingly, in the driver 29A, as illustrated in FIG. 12B, thetransistors 94 in the circuits D0 ₁ to D0 _(M) go into the on state, andthe transistors 95 in the circuits M1 ₁ to M1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the low-levelvoltage VL1, and the output terminating resistance (the outputimpedance) of the driver 29A becomes about 50[Ω]. The same applies to acase where the signals MAINAD and SUBAD related to the previous symbolDS are “1” and “1”, respectively, and the signals MAINAN and SUBANrelated to the current symbol NS are “0” and “1”, respectively.

Moreover, for example, as illustrated in FIG. 9, in a case where thesignals MAINAD and SUBAD related to the previous symbol DS are “1” and“0”, respectively, and the signals MAINAN and SUBAN related to thecurrent symbol NS are “0” and “1”, respectively, the emphasis controller28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “000011”.Accordingly, in the driver 29A, as illustrated in FIG. 12C, thetransistors 94 in the circuits D0 ₁ to D0 _(M) and D1 ₁ to D1 _(N) gointo the on state. As a result, the voltage of the signal SIGA becomesthe low-level voltage VL2, and the output terminating resistance (theoutput impedance) of the driver 29A becomes about 50[Ω].

In this way, the output unit 26 sets respective voltages at the outputterminals ToutA, ToutB, and ToutC on the basis of the current symbol NSand the previous symbol DS. At this time, the transmitting device 10operates like a so-called two-tap FIR (Finite Impulse Response) filterand performs a de-emphasis operation. This makes it possible for thecommunication system 1 to enhance communication performance.

(Receiving Device 30)

As illustrated in FIG. 1, the receiving device 30 includes a receiver 40and a processor 32.

The receiver 40 receives the signals SIGA, SIGB, and SIGC, and generatestransition signals RxF, RxR, and RxP and a clock signal RxCK on thebasis of these signals SIGA, SIGB, and SIGC.

FIG. 13 illustrates a configuration example of the receiver 40. Thereceiver 40 includes resistors 41A, 41B, and 41C, switches 42A, 42B, and42C, amplifiers 43A, 43B, and 43C, a clock generator 44, flip-flops 45and 46, and a signal generator 47.

The resistors 41A, 41B, and 41C serve as a terminating resistor of thecommunication system 1, and a resistance value thereof is about 50[Ω] inthis example. One end of the resistor 41A is coupled to the inputterminal TinA and also to a positive input terminal of the amplifier 43Aand a negative input terminal of the amplifier 43C, and the other end iscoupled to one end of the switch 42A. One end of the resistor 41B iscoupled to the input terminal TinB and also to a positive input terminalof the amplifier 43B and a negative input terminal of the amplifier 43A,and the other end is coupled to one end of the switch 42B. One end ofthe resistor 41C is coupled to the input terminal TinC and also to apositive input terminal of the amplifier 43C and a negative inputterminal of the amplifier 43B, and the other end is coupled to one endof the switch 42C.

The one end of the switch 42A is coupled to the other end of theresistor 41A, and the other end is coupled to the other ends of theswitches 42B and 42C. The one end of the switch 42B is coupled to theother end of the resistor 41B, and the other end is coupled to the otherends of the switches 42A and 42C. The one end of the switch 42C iscoupled to the other end of the resistor 41C, and the other end iscoupled to the other ends of the switches 42A and 42B. In the receivingdevice 30, the switches 42A, 42B, and 42C are set into the on state, andthe resistors 41A to 41C serve as a terminating resistor.

The positive input terminal of the amplifier 43A is coupled to thenegative input terminal of the amplifier 43C and the one end of theresistor 41A and also to the input terminal TinA, and the negative inputterminal is coupled to the positive input terminal of the amplifier 43Band the one end of the resistor 41B and also to the input terminal TinB.The positive input terminal of the amplifier 43B is coupled to thenegative input terminal of the amplifier 43A and the one end of theresistor 41B and also to the input terminal TinB, and the negative inputterminal is coupled to the positive input terminal of the amplifier 43Cand the one end of the resistor 41C and also to the input terminal TinC.The positive input terminal of the amplifier 43C is coupled to thenegative input terminal of the amplifier 43B and the one end of theresistor 41C and also to the input terminal TinC, and the negative inputterminal is coupled to the positive input terminal of the amplifier 43Aand the one end of the resistor 41A and also to the input terminal TinA.

This configuration makes the amplifier 43A output a signal correspondingto a difference AB (SIGA−SIGB) between the signal SIGA and the signalSIGB, and makes the amplifier 43B output a signal corresponding to adifference BC (SIGB−SIGC) between the signal SIGB and the signal SIGC,and makes the amplifier 43C output a signal corresponding to adifference CA (SIGC−SIGA) between the signal SIGC and the signal SIGA.

FIG. 14 illustrates an operation example of the amplifiers 43A, 43B, and43C in a case where the receiver 40 receives the symbol “+x”. It is tobe noted that the switches 42A, 42B, and 42C are in the on state, andare not therefore illustrated. In this example, a voltage state of thesignal SIGA is the voltage state SH; a voltage state of the signal SIGBis the voltage state SL; a voltage state of the signal SIGC is thevoltage state SM. In this case, a current Iin flows to the inputterminal TinA, the resistor 41A, the resistor 41B, and the inputterminal TinB in this order. Then, the positive input terminal of theamplifier 43A is supplied with a voltage corresponding to the voltagestate SH, and the negative input terminal is supplied with a voltagecorresponding to the voltage state SL, and the difference AB becomespositive (AB>0); therefore, the amplifier 43A outputs “1”. Furthermore,the positive input terminal of the amplifier 43B is supplied with avoltage corresponding to the voltage state SL, and the negative inputterminal is supplied with a voltage corresponding to the voltage stateSM, and the difference BC becomes negative (BC<0); therefore, theamplifier 43B outputs “0”. Moreover, the positive input terminal of theamplifier 43C is supplied with a voltage corresponding to the voltagestate SM, and the negative input terminal is supplied with a voltagecorresponding to the voltage state SH, and the difference CA becomesnegative (CA<0); therefore, the amplifier 43C outputs “0”.

The clock generator 44 generates the clock signal RxCK on the basis ofoutput signals of the amplifiers 43A, 43B, and 43C.

The flip-flop 45 outputs respective output signals of the amplifiers43A, 43B, and 43C with a delay of one clock of the clock signal RxCK.The flip-flop 46 outputs three output signals of the flip-flop 45 with adelay of one clock of the clock signal RxCK.

The signal generator 47 generates the transition signals RxF, RxR, andRxP on the basis of the output signals of the flip-flops 45 and 46 andthe clock signal RxCK. These transition signals RxF, RxR, and RxPcorrespond to the transition signals TxF9, TxR9, and TxP9 (FIG. 5) inthe transmitting device 10, respectively, and indicate a symboltransition. The signal generator 47 identifies a symbol transition (FIG.4) on the basis of a symbol indicated by the output signals of theflip-flop 45 and a symbol indicated by the output signals of theflip-flop 46, and generates the transition signals RxF, RxR, and RxP.

The processor 32 (FIG. 1) performs a predetermined process on the basisof transition signals RxF, RxR, and RxP and the clock signal RxCK.

The drivers 29A, 29B, and 29C here correspond to specific examples of a“first driver”, a “second driver”, and a “third driver” in the presentdisclosure, respectively. The drivers 29A, 29B, and 29C correspond to aspecific example of a “driver unit” in the present disclosure. Thesub-driver 290 corresponds to a specific example of a “first sub-driver”in the present disclosure. The sub-driver 291 corresponds to a specificexample of a “second sub-driver” in the present disclosure. Thetransistor 91 in the sub-driver 290 corresponds to a specific example ofa “first switch” in the present disclosure; the transistor 94 in thesub-driver 290 corresponds to a specific example of a “second switch” inthe present disclosure; and the transistor 95 in the sub-driver 290corresponds to a specific example of a “third switch” in the presentdisclosure. The transistor 91 in the sub-driver 291 corresponds to aspecific example of a “fourth switch” in the present disclosure; thetransistor 94 in the sub-driver 291 corresponds to a specific example ofa “fifth switch” in the present disclosure; and the transistor 95 in thesub-driver 291 corresponds to a specific example of a “sixth switch” inthe present disclosure. The emphasis controllers 28A to 28C correspondto a specific example of a “controller” in the present disclosure. Thetransmitting symbol generator 22 corresponds to a specific example of a“signal generator” in the present disclosure. The voltage V1 supplied tothe drain of the transistor 91 corresponds to a specific example of oneof a “first power source” and a “second power source” in the presentdisclosure. The ground voltage supplied to the source of the transistor94 corresponds to a specific example of the other one of the “firstpower source” and the “second power source” in the present disclosure.

[Operation and Working]

Subsequently, operation and working of the communication system 1 of thepresent embodiment are described.

(Outline of Overall Operation)

First, an outline of an overall operation of the communication system 1is described with reference to FIGS. 1, 5, and 7. The clock generator 11of the transmitting device 10 generates the clock signal TxCK. Theprocessor 12 performs a predetermined process, thereby generating thetransition signals TxF0 to TxF6, TxR0 to TxR6, and TxP0 to TxP6. In thetransmitter 20 (FIG. 5), the serializer 21F generates the transitionsignal TxF9 on the basis of the transition signals TxF0 to TxF6 and theclock signal TxCK; the serializer 21R generates the transition signalTxR9 on the basis of the transition signals TxR0 to TxR6 and the clocksignal TxCK; and the serializer 21P generates the transition signal TxP9on the basis of the transition signals TxP0 to TxP6 and the clock signalTxCK. The transmitting symbol generator 22 generates the symbol signalsTx1, Tx2, and Tx3 related to the current symbol NS and the symbolsignals Dtx1, Dtx2, and Dtx3 related to the previous symbol DS on thebasis of the transition signals TxF9, TxR9, and TxP9 and the clocksignal TxCK.

In the output unit 26 (FIG. 7), the voltage generator 50 generates thevoltage Vdc having a voltage corresponding to the medium-level voltageVM0. The driver controller 27N generates the signals MAINAN, SUBAN,MAINBN, SUBBN, MAINCN, and SUBCN on the basis of the symbol signals Tx1,Tx2, and Tx3 related to the current symbol NS and the clock signal TxCK.The driver controller 27D generates the signals MAINAD, SUBAD, MAINBD,SUBBD, MAINCD, and SUBCD on the basis of the symbol signals Dtx1, Dtx2,and Dtx3 related to the previous symbol DS and the clock signal TxCK.The emphasis controller 28A generates the signals UPA0, UPA1, MDA0,MDA1, DNA0, and DNA1 on the basis of the signals MAINAN, SUBAN, MAINAD,and SUBAD. The emphasis controller 28B generates the signals UPB0, UPB1,MDB0, MDB1, DNB0, and DNB1 on the basis of the signals MAINBN, SUBBN,MAINBD and SUBBD. The emphasis controller 28B generates the signalsUPC0, UPC1, MDC0, MDC1, DNC0, and DNC1 on the basis of the signalsMAINCN, SUBCN, MAINCD, and SUBCD. The driver 29A generates the signalSIGA on the basis of the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1.The driver 29B generates the signal SIGB on the basis of the signalsUPB0, UPB1, MDB0, MDB1, DNB0, and DNB1. The driver 29C generates thesignal SIGC on the basis of the signals UPC0, UPC1, MDC0, MDC1, DNC0,and DNC1.

In the receiving device 30 (FIG. 1), the receiver 40 receives thesignals SIGA, SIGB, and SIGC, and generates the transition signals RxF,RxR, and RxP and the clock signal RxCK on the basis of the signals SIGA,SIGB, and SIGC. The processor 32 performs a predetermined process on thebasis of the transition signals RxF, RxR, and RxP and the clock signalRxCK.

(Detailed Operation)

Subsequently, an operation of the transmitting device 10 is described indetail. The output unit 26 of the transmitting device 10 sets respectivevoltages at the output terminals ToutA, ToutB, and ToutC on the basis ofthe current symbol NS and the previous symbol DS.

FIGS. 15 and 16 illustrate the operation in a case where the voltagestate of the signal SIGA makes a transition from the voltage state SH toanother voltage state. FIG. 15 illustrates a change in voltage of thesignal SIGA. FIG. 16 illustrates a transition of an operating state ofthe driver 29A. It is to be noted that the same applies to the signalsSIGB and SIGC. In FIG. 15, 1 UI (Unit Interval) denotes a period totransmit one symbol. Furthermore, ΔV denotes a difference between thehigh-level voltage VH0 and the medium-level voltage VM0 and also adifference between the medium-level voltage VM0 and the low-levelvoltage VL0. The high-level voltage VH0, the medium-level voltage VM0,and the low-level voltage VL0 are reference voltages in a de-emphasisoperation.

In a case where the voltage state of the signal SIGA makes a transitionfrom the voltage state SH to the voltage state SM, the voltage of thesignal SIGA changes from any of the three high-level voltages VH (VH0,VH1, and VH2) to the medium-level voltage VM1minus as illustrated inFIG. 15. Specifically, in this case, the voltage state of the previoussymbol DS is the voltage state SH, thus the signals MAINAD and SUBAD are“1” and “0”, respectively, and the voltage state of the current symbolNS is the voltage state SM, thus the signals MAINAN and SUBAN are, forexample, “0” and “0”, respectively. Therefore, as illustrated in FIG. 9,the emphasis controller 28A sets the signals UPA0, UPA1, MDA0, MDA1,DNA0, and DNA1 to “001001”. Accordingly, in the driver 29A, asillustrated in FIG. 16, the transistors 95 in the circuits M0 ₁ to M0_(M) go into on state, and the transistors 94 in the circuits D1 ₁ to D1_(N) go into the on state. As a result, the voltage of the signal SIGAbecomes the medium-level voltage VM1minus.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SH to the voltage state SM, thevoltage of the signal SIGA is set to the medium-level voltage VM1minus.That is, in this case, a transition amount of the signal SIGA is about(−ΔV) as illustrated in FIG. 15, and therefore, the emphasis controller28A sets a post-transition voltage of the signal SIGA to themedium-level voltage VM1minus that is one step lower than themedium-level voltage VM0 serving as a reference.

Furthermore, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SH to the voltage state SL, thevoltage of the signal SIGA changes from any of the three high-levelvoltages VH (VH0, VH1, and VH2) to the low-level voltage VL2 asillustrated in FIG. 15. Specifically, in this case, the voltage state ofthe previous symbol DS is the voltage state SH, thus the signals MAINADand SUBAD are “1” and “0”, respectively, and the voltage state of thecurrent symbol NS is the voltage state SL, thus the signals MAINAN andSUBAN are “0” and “1”, respectively. Therefore, as illustrated in FIG.9, the emphasis controller 28A sets the signals UPA0, UPA1, MDA0, MDA1,DNA0, and DNA1 to “000011”. Accordingly, in the driver 29A, asillustrated in FIG. 16, the transistors 94 in the circuits D0 ₁ to D0_(M) and D1 ₁ to D1 _(N) go into the on state. As a result, the voltageof the signal SIGA becomes the low-level voltage VL2.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SH to the voltage state SL, thevoltage of the signal SIGA is set to the low-level voltage VL2. That is,in this case, the transition amount of the signal SIGA is about (−2ΔV)as illustrated in FIG. 15, and therefore, the emphasis controller 28Asets the post-transition voltage of the signal SIGA to the low-levelvoltage VL2 that is two step lower than the low-level voltage VL0serving as a reference.

It is to be noted that in a case where the voltage state of the signalSIGA is maintained in the voltage state SH, the voltage of the signalSIGA changes from any of the three high-level voltages VH (VH0, VH1, andVH2) to the high-level voltage VH0 as illustrated in FIG. 15.Specifically, in this case, the voltage state of the previous symbol DSis the voltage state SH, thus the signals MAINAD and SUBAD are “1” and“0”, respectively, and the voltage state of the current symbol NS is thevoltage state SH, thus the signals MAINAN and SUBAN are “1” and “0”,respectively. Therefore, as illustrated in FIG. 9, the emphasiscontroller 28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1to “100001”. Accordingly, in the driver 29A, as illustrated in FIG. 16,the transistors 91 in the circuits U0 ₁ to U0 _(M) go into on state, andthe transistors 94 in the circuits D1 ₁ to D1 _(N) go into the on state.As a result, the voltage of the signal SIGA becomes the high-levelvoltage VH0. In this way, in the transmitting device 10, in a case wherethe voltage state of the signal SIGA is maintained in the voltage stateSH over multiple unit intervals, the voltage of the signal SIGA is setto the high-level voltage VH0 in the second and subsequent unitintervals. That is, this high-level voltage VH0 is a de-emphasizedvoltage.

FIGS. 17 and 18 illustrate an operation in a case where the voltagestate of the signal SIGA makes a transition from the voltage state SM toanother voltage state. FIG. 17 illustrates a change in voltage of thesignal SIGA. FIG. 18 illustrates a transition of the operating state ofthe driver 29A.

In a case where the voltage state of the signal SIGA makes a transitionfrom the voltage state SM to the voltage state SH, the voltage of thesignal SIGA changes from any of the three medium-level voltages VM (VM0,VM1plus, and VM1minus) to the high-level voltage VH1 as illustrated inFIG. 17. Specifically, in this case, the voltage state of the previoussymbol DS is the voltage state SM, thus the signals MAINAD and SUBADare, for example, “0” and “0”, respectively, and the voltage state ofthe current symbol NS is the voltage state SH, thus the signals MAINANand SUBAN are “1” and “0”, respectively. Therefore, as illustrated inFIG. 9, the emphasis controller 28A sets the signals UPA0, UPA1, MDA0,MDA1, DNA0, and DNA1 to “100100”. Accordingly, in the driver 29A, asillustrated in FIG. 18, the transistors 91 in the circuits U0 ₁ to U0_(M) go into the on state, and the transistors 95 in the circuits M1 ₁to M1 _(N) go into the on state. As a result, the voltage of the signalSIGA becomes the high-level voltage VH1.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SM to the voltage state SH, thevoltage of the signal SIGA is set to the high-level voltage VH1. Thatis, in this case, the transition amount of the signal SIGA is about(+ΔV) as illustrated in FIG. 17, and therefore, the emphasis controller28A sets the post-transition voltage of the signal SIGA to thehigh-level voltage VH1 that is one step higher than the high-levelvoltage VH0 serving as a reference.

Furthermore, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SM to the voltage state SL, thevoltage of the signal SIGA changes from any of the three medium-levelvoltages VM (VM0, VM1plus, and VM1minus) to the low-level voltage VL1 asillustrated in FIG. 17. Specifically, in this case, the voltage state ofthe previous symbol DS is the voltage state SM, thus the signals MAINADand SUBAD are, for example, “0” and “0”, respectively, and the voltagestate of the current symbol NS is the voltage state SL, thus the signalsMAINAN and SUBAN are “0” and “1”, respectively. Therefore, asillustrated in FIG. 9, the emphasis controller 28A sets the signalsUPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “000110”. Accordingly, in thedriver 29A, as illustrated in FIG. 18, the transistors 94 in thecircuits D0 ₁ to D0 _(M) go into the on state, and the transistors 95 inthe circuits M1 ₁ to M1 _(N) go into the on state. As a result, thevoltage of the signal SIGA becomes the low-level voltage VL1.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SM to the voltage state SL, thevoltage of the signal SIGA is set to the low-level voltage VL1. That is,in this case, the transition amount of the signal SIGA is about (−ΔV) asillustrated in FIG. 17, and therefore, the emphasis controller 28A setsthe post-transition voltage of the signal SIGA to the low-level voltageVL1 that is one step lower than the low-level voltage VL0 serving as areference.

It is to be noted that in a case where the voltage state of the signalSIGA is maintained in the voltage state SM, the voltage of the signalSIGA changes from any of the three medium-level voltages VM (VM0,VM1plus, and VM1minus) to the medium-level voltage VM0 as illustrated inFIG. 17. Specifically, in this case, the voltage state of the previoussymbol DS is the voltage state SM, thus the signals MAINAD and SUBADare, for example, “0” and “0”, respectively, and the voltage state ofthe current symbol NS is the voltage state SM, thus the signals MAINANand SUBAN are, for example, “0” and “0”, respectively. Therefore, asillustrated in FIG. 9, the emphasis controller 28A sets the signalsUPA0, UPA1, MDA0, MDA1, DNA0, and DNA1 to “001100”. Accordingly, in thedriver 29A, as illustrated in FIG. 18, the transistors 95 in thecircuits M0 ₁ to M0 _(M) and M1 ₁ to M1 _(N) go into the on state. As aresult, the voltage of the signal SIGA becomes the medium-level voltageVM0. In this way, in the transmitting device 10, in a case where thevoltage state of the signal SIGA is maintained in the voltage state SMover multiple unit intervals, the voltage of the signal SIGA is set tothe medium-level voltage VM0 in the second and subsequent unitintervals. That is, this medium-level voltage VM0 is a de-emphasizedvoltage.

FIGS. 19 and 20 illustrate an operation in a case where the voltagestate of the signal SIGA makes a transition from the voltage state SL toanother voltage state. FIG. 19 illustrates a change in voltage of thesignal SIGA. FIG. 20 illustrates a transition of the operating state ofthe driver 29A.

In a case where the voltage state of the signal SIGA makes a transitionfrom the voltage state SL to the voltage state SM, the voltage of thesignal SIGA changes from any of the three low-level voltages VL (VL0,VL1, and VL2) to the medium-level voltage VM1plus as illustrated in FIG.19. Specifically, in this case, the voltage state of the previous symbolDS is the voltage state SL, thus the signals MAINAD and SUBAD are “0”and “1”, respectively, and the voltage state of the current symbol NS isthe voltage state SM, thus the signals MAINAN and SUBAN are, forexample, “0” and “0”, respectively. Therefore, as illustrated in FIG. 9,the emphasis controller 28A sets the signals UPA0, UPA1, MDA0, MDA1,DNA0, and DNA1 to “011000”. Accordingly, in the driver 29A, asillustrated in FIG. 20, the transistors 95 in the circuits M0 ₁ to M0_(M) go into the on state, and the transistors 91 in the circuits U1 ₁to U1 _(N) go into the on state. As a result, the voltage of the signalSIGA becomes the medium-level voltage VM1plus.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SL to the voltage state SM, thevoltage of the signal SIGA is set to the medium-level voltage VM1plus.That is, in this case, the transition amount of the signal SIGA is about(+ΔV) as illustrated in FIG. 19, and therefore, the emphasis controller28A sets the post-transition voltage of the signal SIGA to themedium-level voltage VM1plus that is one step higher than the referencemedium-level voltage VM0.

Furthermore, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SL to the voltage state SH, thevoltage of the signal SIGA changes from any of the three low-levelvoltages VL (VL0, VL1, and VL2) to the high-level voltage VH2 asillustrated in FIG. 19. Specifically, in this case, the voltage state ofthe previous symbol DS is the voltage state SL, thus the signals MAINADand SUBAD are “0” and “1”, respectively, and the voltage state of thecurrent symbol NS is the voltage state SH, thus the signals MAINAN andSUBAN are “1” and “0”, respectively. Therefore, as illustrated in FIG.9, the emphasis controller 28A sets the signals UPA0, UPA1, MDA0, MDA1,DNA0, and DNA1 to “110000”. Accordingly, in the driver 29A, asillustrated in FIG. 20, the transistors 91 in the circuits U0 ₁ to U0_(M) and U1 ₁ to U1 _(N) go into the on state. As a result, the voltageof the signal SIGA becomes the high-level voltage VH2.

In this way, in a case where the voltage state of the signal SIGA makesa transition from the voltage state SL to the voltage state SH, thevoltage of the signal SIGA is set to the high-level voltage VH2. Thatis, in this case, the transition amount of the signal SIGA is about(+2ΔV) as illustrated in FIG. 19, and therefore, the emphasis controller28A sets the post-transition voltage of the signal SIGA to thehigh-level voltage VH2 that is two steps higher than the high-levelvoltage VH0 serving as a reference.

It is to be noted that in a case where the voltage state of the signalSIGA is maintained in the voltage state SL, the voltage of the signalSIGA changes from any of the three low-level voltages VL (VL0, VL1, andVL2) to the low-level voltage VL0 as illustrated in FIG. 19.Specifically, in this case, the voltage state of the previous symbol DSis the voltage state SL, thus the signals MAINAD and SUBAD are “0” and“1”, respectively, and the voltage state of the current symbol NS is thevoltage state SL, thus the signals MAINAN and SUBAN are “0” and “1”,respectively. Therefore, as illustrated in FIG. 9, the emphasiscontroller 28A sets the signals UPA0, UPA1, MDA0, MDA1, DNA0, and DNA1to “010010”. Accordingly, in the driver 29A, as illustrated in FIG. 20,the transistors 94 in the circuits D0 ₁ to D0 _(M) go into the on state,and the transistors 91 in the circuits U1 ₁ to U1 _(N) go into the onstate. As a result, the voltage of the signal SIGA becomes the low-levelvoltage VL0. In this way, in the transmitting device 10, in a case wherethe voltage state of the signal SIGA is maintained in the voltage stateSL over multiple unit intervals, the voltage of the signal SIGA is setto the low-level voltage VL0 in the second and subsequent unitintervals. That is, this low-level voltage VL0 is a de-emphasizedvoltage.

In this way, with respect to each of the signals SIGA, SIGB, and SIGC,the transmitting device 10 sets the post-transition voltage inaccordance with a voltage transition amount associated with a transitionof the voltage state. Specifically, in a case where the voltage statemakes a transition to a state one step higher, the transmitting device10 sets the post-transition voltage to a voltage one step higher than areference voltage (for example, the medium-level voltage VM0 or thehigh-level voltage VH0). That is, in this case, the transmitting device10 sets an emphasis voltage that is one step more positive. Furthermore,in a case where the voltage state makes a transition to a state twosteps higher, the transmitting device 10 sets the post-transitionvoltage to a voltage two steps higher than the reference voltage (forexample, the high-level voltage VH0). That is, in this case, thetransmitting device 10 sets an emphasis voltage that is two steps morepositive. Moreover, in a case where the voltage state makes a transitionto a state one step lower, the transmitting device 10 sets thepost-transition voltage to a voltage one step lower than the referencevoltage (for example, the medium-level voltage VM0 or the low-levelvoltage VL0). That is, in this case, the transmitting device 10 sets anemphasis voltage that is one step more negative. Furthermore, in a casewhere the voltage state makes a transition to a state two steps lower,the transmitting device 10 sets the post-transition voltage to a voltagetwo steps lower than the reference voltage (for example, the low-levelvoltage VL0). That is, in this case, the transmitting device 10 sets anemphasis voltage that is two steps more negative. In this way, withrespect to each of signals SIGA, SIGB, and SIGC, the transmitting device10 sets an emphasis voltage in accordance with the voltage transitionamount so as to be proportional to the transition amount.

FIGS. 21A to 21E illustrate an operation example of the communicationsystem 1 in a case where the symbol “+x” makes a transition to a symbolother than “+x”. FIG. 21A illustrates a case of a symbol transition from“+x” to “−x”; FIG. 21B illustrates a case of a symbol transition from“+x” to “+y”; FIG. 21C illustrates a case of a symbol transition from“+x” to “−y”; FIG. 21D illustrates a case of a symbol transition from“+x” to “+z”; FIG. 21E illustrates a case of a symbol transition from“+x” to “−z”. In each of FIGS. 21A to 21E, (A) illustrates respectivewaveforms of signals SIGA, SIGB, and SIGC at the output terminals ToutA,ToutB, and ToutC of the transmitting device 10, and (B) illustratesrespective waveforms of differences AB, BC, and CA in the receivingdevice 30. Furthermore, a solid line indicates a waveform in a casewhere a de-emphasis operation has been performed, and a broken lineindicates a waveform in a case where a de-emphasis operation is notperformed. Moreover, the voltage of the signal SIGA before thetransition is any of the three high-level voltages VH (VH0, VH1, andVH2); however, for convenience of illustration, the voltage of thesignal SIGA is the high-level voltage VH0 in these figures. Likewise, avoltage of the signal SIGB before the transition is the low-levelvoltage VL0, and a voltage of the signal SIGC before the transition isthe medium-level voltage VM0.

In a case of a symbol transition from “+x” to “−x”, as illustrated in(A) of FIG. 21A, the signal SIGA changes from the high-level voltage VH0to the low-level voltage VL2; the signal SIGB changes from the low-levelvoltage VL0 to the high-level voltage VH2; and the signal SIGC ismaintained in the medium-level voltage VM0. That is, a transition amountof the signal SIGA is about (−2ΔV); therefore, the transmitting device10 sets the voltage of the signal SIGA to the low-level voltage VL2 thatis two steps lower than the low-level voltage VL0 serving as areference. Furthermore, a transition amount of the signal SIGB is about(+2ΔV); therefore, the transmitting device 10 sets the voltage of thesignal SIGB to the high-level voltage VH2 that is two steps higher thanthe high-level voltage VH0 serving as a reference. At this time, asillustrated in (B) of FIG. 21A, a transition amount of the difference AB(SIGA−SIGB) is about (−4ΔV); therefore, the difference AB after thetransition becomes four steps lower than that in a case where ade-emphasis operation is not performed. Furthermore, a transition amountof the difference BC (SIGB−SIGC) is about (+2ΔV); therefore, thedifference BC after the transition becomes two steps higher than that ina case where a de-emphasis operation is not performed. Moreover, atransition amount of the difference CA (SIGC−SIGA) is about (+2ΔV);therefore, the difference CA after the transition becomes two stepshigher than that in a case where a de-emphasis operation is notperformed.

In a case of a symbol transition from “+x” to “+y”, as illustrated in(A) of FIG. 21B, the signal SIGA changes from the high-level voltage VH0to the medium-level voltage VM1minus; the signal SIGB changes from thelow-level voltage VL0 to the high-level voltage VH2; and the signal SIGCchanges from the medium-level voltage VM0 to the low-level voltage VL1.That is, the transition amount of the signal SIGA is about (−ΔV);therefore, the transmitting device 10 sets the voltage of the signalSIGA to the medium-level voltage VM1minus that is one step lower thanthe medium-level voltage VM0 serving as a reference. Furthermore, thetransition amount of the signal SIGB is about (+2ΔV); therefore, thetransmitting device 10 sets the voltage of the signal SIGB to thehigh-level voltage VH2 that is two steps higher than the high-levelvoltage VH0 serving as a reference. Moreover, the transition amount ofthe signal SIGC is about (−ΔV); therefore, the transmitting device 10sets the voltage of the signal SIGC to the low-level voltage VL1 that isone step lower than the low-level voltage VL0 serving as a reference. Atthis time, as illustrated in (B) of FIG. 21B, the transition amount ofthe difference AB (SIGA−SIGB) is about (−3ΔV); therefore, the differenceAB after the transition becomes three steps lower than that in a casewhere a de-emphasis operation is not performed. Furthermore, thetransition amount of the difference BC (SIGB−SIGC) is about (+3ΔV);therefore, the difference BC after the transition becomes three stepshigher than that in a case where a de-emphasis operation is notperformed.

In a case of a symbol transition from “+x” to “−y”, as illustrated in(A) of FIG. 21C, the signal SIGA changes from the high-level voltage VH0to the medium-level voltage VM1minus; the signal SIGB is maintained inthe low-level voltage VL0; the signal SIGC changes from the medium-levelvoltage VM0 to the high-level voltage VH1. That is, the transitionamount of the signal SIGA is about (−ΔV); therefore, the transmittingdevice 10 sets the voltage of the signal SIGA to the medium-levelvoltage VM1minus that is one step lower than the medium-level voltageVM0 serving as a reference. Furthermore, the transition amount of thesignal SIGC is about (+ΔV); therefore, the transmitting device 10 setsthe voltage of the signal SIGC to the high-level voltage VH1 that is onestep higher than the high-level voltage VH0 serving as a reference. Atthis time, as illustrated in (B) of FIG. 21C, the transition amount ofthe difference AB (SIGA−SIGB) is about (−ΔV); therefore, the differenceAB after the transition becomes one step lower than that in a case wherea de-emphasis operation is not performed. Furthermore, the transitionamount of the difference BC (SIGB−SIGC) is about (−ΔV); therefore, thedifference BC after the transition becomes one step lower than that in acase where a de-emphasis operation is not performed. Moreover, thetransition amount of the difference CA (SIGC−SIGA) is about (+2ΔV);therefore, the difference CA after the transition becomes two stepshigher than that in a case where a de-emphasis operation is notperformed.

In a case of a symbol transition from “+x” to “+z”, as illustrated in(A) of FIG. 21D, the signal SIGA changes from the high-level voltage VH0to the low-level voltage VL2; the signal SIGB changes from the low-levelvoltage VL0 to the medium-level voltage VM1plus; and the signal SIGCchanges from the medium-level voltage VM0 to the high-level voltage VH1.That is, the transition amount of the signal SIGA is about (−2ΔV);therefore, the transmitting device 10 sets the voltage of the signalSIGA to the low-level voltage VL2 that is two steps lower than thelow-level voltage VL0 serving as a reference. Furthermore, thetransition amount of the signal SIGB is about (+ΔV); therefore, thetransmitting device 10 sets the voltage of the signal SIGB to themedium-level voltage VM1plus that is one step higher than themedium-level voltage VM0 serving as a reference. Moreover, thetransition amount of the signal SIGC is about (+ΔV); therefore, thetransmitting device 10 sets the voltage of the signal SIGC to thehigh-level voltage VH1 that is one step higher than the high-levelvoltage VH0 serving as a reference. At this time, as illustrated in (B)of FIG. 21D, the transition amount of the difference AB (SIGA−SIGB) isabout (−3ΔV); therefore, the difference AB after the transition becomesthree steps lower than that in a case where a de-emphasis operation isnot performed. Furthermore, a transition amount of the difference CA(SIGC−SIGA) is about (+3ΔV); therefore, the difference CA after thetransition becomes three steps higher than that in a case where ade-emphasis operation is not performed.

In a case of a symbol transition from “+x” to “−z”, as illustrated in(A) of FIG. 21E, the signal SIGA is maintained in the high-level voltageVH0; the signal SIGB changes from the low-level voltage VL0 to themedium-level voltage VM1plus; and the signal SIGC changes from themedium-level voltage VM0 to the low-level voltage VL1. That is, thetransition amount of the signal SIGB is about (+ΔV); therefore, thetransmitting device 10 sets the voltage of the signal SIGB to themedium-level voltage VM1plus that is one step higher than themedium-level voltage VM0 serving as a reference. Furthermore, thetransition amount of the signal SIGC is about (−ΔV); therefore, thetransmitting device 10 sets the voltage of the signal SIGC to thelow-level voltage VL1 that is one step lower than the low-level voltageVL0 serving as a reference. At this time, as illustrated in (B) of FIG.21E, the transition amount of the difference AB (SIGA−SIGB) is about(−ΔV); therefore, the difference AB after the transition becomes onestep lower than that in a case where a de-emphasis operation is notperformed. Furthermore, the transition amount of the difference BC(SIGB−SIGC) is about (+2ΔV); therefore, the difference BC after thetransition becomes two steps higher than that in a case where ade-emphasis operation is not performed. Moreover, the transition amountof the difference CA (SIGC−SIGA) is about (−ΔV); therefore, thedifference CA after the transition becomes one step lower than that in acase where a de-emphasis operation is not performed.

In this way, in the communication system 1, with respect to each ofsignals SIGA, SIGB, and SIGC, an emphasis voltage is set in accordancewith the voltage transition amount. That is, the transmitting device 10performs a de-emphasis operation on each of the signals SIGA, SIGB, andSIGC (single-ended signals). As a result, the communication system 1makes it possible to enhance waveform quality of each of the signalsSIGA, SIGB, and SIGC; therefore, it is possible to enhance communicationperformance.

Furthermore, in the communication system 1, the emphasis voltage is setwith respect to each of the signals SIGA, SIGB, and SIGC in this way;therefore, also with respect to each of differences AB, BC, and CA thatare differential signals, an emphasis voltage is set in accordance withthe voltage transition amount. As a result, the communication system 1makes it possible to enhance waveform quality of each of the differencesAB, BC, and CA as well; therefore, it is possible to enhancecommunication performance.

FIG. 22 illustrates an eye diagram of the difference AB between thesignals SIGA and SIGB, the difference BC between the signals SIGB andSIGC, and the difference CA between the signals SIGC and SIGA in a casewhere a de-emphasis operation has been performed. FIG. 23 illustrates aneye diagram of the differences AB, BC, and CA in a case where thede-emphasis operation is not performed. In the communication system 1,even in a case where the transmission line 100 is long, as illustratedin FIGS. 22 and 23, an eye opening is able to be extended throughperforming a de-emphasis operation, and as a result, it is possible toenhance communication performance.

Furthermore, in the communication system 1, for example, the driver 29Ais provided with the circuits M0 ₁ to M0 _(M) and M1 ₁ to M1 _(M), and,for example, in a case where the voltage state of the output terminalToutA is set to the voltage state SM, the transistors 95 in the circuitsM0 ₁ to M0 _(M) are put into the on state (FIGS. 11A to 11C). Then, in acase where the voltage at the output terminal ToutA is set to themedium-level voltage VM1plus (FIG. 11A), the transistors 91 in thecircuits U1 ₁ to U1 _(N) are put into the on state; in a case where thevoltage at the output terminal ToutA is set to the medium-level voltageVM0 (FIG. 11B), the transistors 95 in the circuits M1 ₁ to M1 _(M) areput into the on state; and in a case where the voltage at the outputterminal ToutA is set to the medium-level voltage VM1minus (FIG. 11C),the transistors 94 in the circuits D1 ₁ to D1 _(M) are put into the onstate. Accordingly, it is possible to reduce power consumption ascompared with a comparative example described below.

Comparative Example

Subsequently, workings of the present embodiment is described incomparison with a comparative example. A communication system 1Raccording to the comparative example includes a transmitting device 10R.The transmitting device 10R includes a transmitter 20R. This transmitter20R includes an output unit 26R, as with the transmitter 20 (FIG. 5)according to the present embodiment.

FIG. 24 illustrates a configuration example of the output unit 26R. Theoutput unit 26R includes emphasis controllers 28RA, 28RB, and 28RC anddrivers 29RA, 29RB, and 29RC. The emphasis controller 28RA generateseight signals UPAA0, UPAB0, UPAA1, UPAB1, DNAA0, DNAB0, DNAA1, and DNAB1on the basis of signals MAINAN and SUBAN and signals MAINAD and SUBAD.The driver 29RA generates a signal SIGA on the basis of the eightsignals UPAA0, UPAB0, UPAA1, UPAB1, DNAA0, DNAB0, DNAA1, and DNAB1. Thesame applies to the emphasis controller 28RB and the driver 29RB and tothe emphasis controller 28RC and the driver 29RC.

FIG. 25 illustrates a configuration example of the driver 29RA. The sameapplies to the drivers 29RB and 29RC. The driver 29RA includes Kcircuits UA0 (circuits UA0 ₁ to UA0 _(K)), L circuits UB0 (circuits UB0₁ to UB0 _(L)), K circuits UA1 (circuits UA1 ₁ to UA1 _(K)), L circuitsUB1 (circuits UB1 ₁ to UB1 _(L)), K circuits DA0 (circuits DA0 ₁ to DA0_(K)), L circuits DB0 (circuits DB0 ₁ to DB0 _(L)), K circuits DA1(circuits DA1 ₁ to DA1 _(K)), and L circuits DB1 (circuits DB1 ₁ to DB1_(L)). In this example, “K” is a number greater than “L”.

The circuits UA0 ₁ to UA0 _(K), UB0 ₁ to UB0 _(L), UA1 ₁ to UA1 _(K),and UB1 ₁ to UB1 _(L) each include the transistor 91 and the resistor92, as with the circuits U0 ₁ to U0 _(M) and U1 ₁ to U1 _(N) accordingto the present embodiment. The gates of the transistors 91 in thecircuits UA0 ₁ to UA0 _(K) are supplied with the signal UPAA0; the gatesof the transistors 91 in the circuits UB0 ₁ to UB0 _(L) are suppliedwith the signal UPAB0; the gates of the transistors 91 in the circuitsUA1 ₁ to UA1 _(K) are supplied with the signal UPAA1; and the gates ofthe transistors 91 in the circuits UB1 ₁ to UB1 _(L) are supplied withthe signal UPAB1. The sum of an on-state resistance value of thetransistor 91 and a resistance value of the resistor 92 is“50×(2×K+2×L)”[Ω] in this example.

The circuits DA0 ₁ to DA0 _(K), DB0 ₁ to DB0 _(L), DA1 ₁ to DA1 _(K),and DB1 ₁ to DB1 _(L) each include the resistor 93 and the transistor94, as with the circuits D0 ₁ to D0 _(M) and D1 ₁ to D1 _(N) accordingto the present embodiment. The gates of the transistors 94 in thecircuits DA0 ₁ to DA0 _(K) are supplied with the signal DNAA0; the gatesof the transistors 94 in the circuits DB0 ₁ to DB0 _(L) are suppliedwith the signal DNAB0; the gates of the transistors 94 in the circuitsDA1 ₁ to DA1 _(K) are supplied with the signal DNAA1; and the gates ofthe transistors 94 in the circuits DB1 ₁ to DB1 _(L) are supplied with asignal DNAB1. The sum of a resistance value of the resistor 93 and anon-state resistance value of the transistor 94 is “50×(2×K+2×L)”[Ω] inthis example.

FIGS. 26A to 26C illustrate an operation example of the driver 29RA in acase where the signal SIGA is set to the voltage state SH. FIGS. 27A to27C illustrate an operation example of the driver 29RA in a case wherethe signal SIGA is set to the voltage state SM. FIGS. 28A to 28Cillustrate an operation example of the driver 29RA in a case where asignal SIGA is set to the voltage state SL.

In this example, in a case where the signal SIGA is set to thehigh-level voltage VH2, as illustrated in FIG. 26A, the transistors 91in the circuits UA0 ₁ to UA0 _(K), UB0 ₁ to UB0 _(L), UA1 ₁ to UA1 _(K),and UB1 ₁ to UB1 _(L) are put into the on state. Furthermore, in a casewhere the signal SIGA is set to the high-level voltage VH1, asillustrated in FIG. 26B, the transistors 91 in the circuits UA0 ₁ to UA0_(K), UA1 ₁ to UA1 _(K), and UB1 ₁ to UB1 _(L) are put into the onstate, and the transistors 94 in the circuits DB1 ₁ to DB1 _(L) are putinto the on state. Moreover, in a case where the signal SIGA is set tothe high-level voltage VH0, as illustrated in FIG. 26C, the transistors91 in the circuits UA0 ₁ to UA0 _(K) and UA1 ₁ to UA1 _(K) are put intothe on state, and the transistors 94 in the circuits DB0 ₁ to DB0 _(L)and DB1 ₁ to DB1 _(L) are put into the on state.

In a case where the signal SIGA is set to the medium-level voltageVM1plus, as illustrated in FIG. 27A, the transistors 91 in the circuitsUA0 ₁ to UA0 _(K), UB0 ₁ to UB0 _(L), and UB1 ₁ to UB1 _(L) are put intothe on state, and the transistors 94 in the circuits DA0 ₁ to DA0 _(K)are put into the on state. Furthermore, in a case where the signal SIGAis set to the medium-level voltage VM0, as illustrated in FIG. 27B, thetransistors 91 in the circuits UA0 ₁ to UA0 _(K) and UB0 ₁ to UB0 _(L)are put into the on state, and the transistors 94 in the circuits DA0 ₁to DA0 _(K) and DB0 ₁ to DB0 _(L) are put into the on state. Moreover,in a case where the signal SIGA is set to the medium-level voltageVM1minus, as illustrated in FIG. 27C, the transistors 91 in the circuitsUA0 ₁ to UA0 _(K) are put into the on state, and the transistors 94 inthe circuits DA0 ₁ to DA0 _(K), DB0 ₁ to DB0 _(L), and DB1 ₁ to DB1 _(L)are put into the on state.

In a case where the signal SIGA is set to the low-level voltage VL0, asillustrated in FIG. 28A, the transistors 91 in the circuits UB0 ₁ to UB0_(L) and UB1 ₁ to UB1 _(L) are put into the on state, and thetransistors 94 in the circuits DA0 ₁ to DA0 _(K) and DA1 ₁ to DA1 _(K)are put into the on state. Furthermore, in a case where the signal SIGAis set to the low-level voltage VL1, as illustrated in FIG. 28B, thetransistors 91 in the circuits UB0 ₁ to UB0 _(L) are put into the onstate, and the transistors 94 in the circuits DA0 ₁ to DA0 _(K), DB0 ₁to DB0 _(L), and DA1 ₁ to DA1 _(K) are put into the on state. Moreover,in a case where the signal SIGA is set to the low-level voltage VL2, asillustrated in FIG. 28C, the transistors 94 in the circuits DA0 ₁ to DA0_(K), DB0 ₁ to DB0 _(L), DA1 ₁ to DA1 _(K), and DB1 ₁ to DB1 _(L) areput into the on state.

In this way, in the communication system 1R according to the comparativeexample, for example, in a case where the voltage at the output terminalToutA is set to the medium-level voltage VM0 (FIG. 27B), the transistors91 in the circuits UA0 ₁ to UA0 _(K) and UB0 ₁ to UB0 _(L) are put intothe on state, and the transistors 94 in the circuits DA0 ₁ to DA0 _(K)and DB0 ₁ to DB0 _(L) are put into the on state. In this way, the driver29A sets the voltage at the output terminal ToutA with Thevenintermination. This Thevenin termination allows a large amount of currentcaused by a potential difference between the voltage V1 and the groundvoltage to flow. A series resistance value of the Thevenin terminationis about 100[Ω]. The same applies to a case where the voltage at theoutput terminal ToutA is set to the medium-level voltages VM1plus andVM1minus (FIGS. 27A and 27C). Therefore, in the communication system 1R,a large amount of current flows by the Thevenin termination, and as aresult, power consumption is increased.

In contrast, in the communication system 1 according to the embodiment,for example, in a case where the voltage at the output terminal ToutA isset to the medium-level voltage VM0 (FIG. 11B), the transistors 95 inthe circuits M0 ₁ to M0 _(M) and M1 ₁ to M1 _(M) are put into the onstate. That is, the voltage at the output terminal ToutA is set with useof the voltage Vdc generated by the voltage generator 50, instead ofsetting the voltage at the output terminal ToutA with Thevenintermination. Furthermore, for example, in a case where the voltage atthe output terminal ToutA is set to the medium-level voltage VM1plus(FIG. 11A), the transistors 95 in the circuits M0 ₁ to M0 _(M) are putinto the on state, and the transistors 91 in the circuits U1 ₁ to U1_(M) are put into the on state. In this case, current flows from thecircuits U1 ₁ to U1 _(M) to the circuits M0 ₁ to M0 _(M). However, thiscurrent is smaller than the current in the case of the comparativeexample (FIG. 27A). That is, firstly, this current flows by a potentialdifference between the voltage V1 and the voltage Vdc, unlike in thecase of the comparative example. That is, this potential difference isabout a half of that in the case of the comparative example. Then,secondly, the impedance of the circuits U1 ₁ to U1 _(m) is sufficientlygreater than that of the circuits M0 ₁ to M0 _(M), and a seriesresistance value is therefore sufficiently greater than 100[Ω]. As aresult, this current becomes smaller than that in the case of thecomparative example (FIG. 27A). The same applies to a case where thevoltage at the output terminal ToutA is set to the medium-level voltageVM1minus (FIG. 11C). Consequently, the communication system 1 makes itpossible to reduce power consumption.

[Effects]

As described above, in the present embodiment, the sub-driver 290 isprovided with the circuits M0 ₁ to M0 _(M), and, for example, in a casewhere the voltage state of the output terminal ToutA is set to thevoltage state SM, the transistors 95 in the circuits M0 ₁ to M0 _(M) areput into the on state. This makes it possible to reduce powerconsumption.

In the present embodiment, the sub-driver 291 adjusts the voltage ineach voltage state to set an emphasis voltage, which makes it possibleto enhance communication performance.

In the present embodiment, with respect to each of the signals SIGA,SIGB, and SIGC, an emphasis voltage is set in accordance with thevoltage transition amount, which makes it possible to enhance waveformquality of each of the signals SIGA, SIGB, and SIGC and therefore toenhance communication performance.

Modification Example 1

In the above-described embodiment, the drivers 29A, 29B, and 29C areconfigured as illustrated in FIG. 8; however, the drivers 29A, 29B, and29C are not limited thereto. This modification example are describedbelow with reference to some examples.

FIG. 29 illustrates a configuration example of a driver 39A according tothe present modification example. This driver 39A corresponds to thedriver 29A according to the above-described embodiment. The driver 39includes two sub-drivers 390 and 391. The sub-drivers 390 and 391 are amodification of the sub-drivers 290 and 291 (FIG. 8) according to theabove-described embodiment, and adopt a modified form of coupling of thetransistor 91 and the resistor 92. In each of the circuits U0 ₁ to U0_(M) and U1 ₁ to U1 _(N), one end of the resistor 92 is supplied withthe voltage V1, and the other end is coupled to the drain of thetransistor 91. In each of the circuits U0 ₁ to U0 _(M), the gate of thetransistor 91 is supplied with the signal UPA0, and the drain is coupledto the other end of the resistor 92, and the source is coupled to theoutput terminal ToutA. In each of the circuits U1 ₁ to U1 _(N), the gateof the transistor 91 is supplied with the signal UPA1, and the drain iscoupled to the other end of the resistor 92, and the source is coupledto the output terminal ToutA.

FIG. 30 illustrates a configuration example of another driver 49Aaccording to the present modification example. This driver 49Acorresponds to the driver 29A according to the above-describedembodiment. The driver 49A includes two sub-drivers 490 and 491. Thesub-driver 490 includes M circuits C0 (circuits C0 ₁ to C0 _(M)). Thesub-driver 491 includes N circuits C1 (circuits C1 ₁ to C1 _(N)). Thecircuits C0 ₁ to C0 _(M) and C1 ₁ to C1 _(N) each include resistors 92and 97 and the transistors 91, 94, and 95.

First, the circuits C0 ₁ to C0 _(M) are described. In each of thecircuits C0 ₁ to C0 _(M), one end of the resistor 92 is supplied withthe voltage V1, and the other end is coupled to the drain of thetransistor 91. The gate of the transistor 91 is supplied with the signalUPA0, and the drain is coupled to the other end of the resistor 92, andthe source is coupled to one end of the resistor 97 and the outputterminal ToutA. The one end of the resistor 97 is coupled to the sourceof the transistor 91 and the output terminal ToutA, and the other end iscoupled to the drains of the transistors 94 and 95. The gate of thetransistor 94 is supplied with the signal DNA0, and the drain is coupledto the other end of the resistor 97 and the drain of the transistor 95,and the source is grounded. The gate of the transistor 95 is suppliedwith the signal MDA0, and the source is supplied with the voltage Vdcgenerated by the voltage generator 50, and the drain is coupled to theother end of the resistor 97 and the drain of the transistor 94.

Next, the circuits C1 ₁ to C1 _(N) are described. In each of thecircuits C1 ₁ to C1 _(N), the gate of the transistor 91 is supplied withthe signal UPA1. The gate of the transistor 94 is supplied with thesignal DNA1. The gate of the transistor 95 is supplied with the signalMDA1. Except for these, the circuits C1 ₁ to C1 _(N) are similar to thecircuits C0 ₁ to C0 _(M).

In this driver 49A, the resistor 97 corresponds to the resistors 93 and96 in the driver 29A (FIG. 8) according to the above-describedembodiment. That is, for example, in the sub-driver 490, in a case wherethe transistor 94 goes into the on state, a resistance value of theresistor 97 and an on-resistance of the transistor 94 constitute anoutput impedance of the sub-driver 490, and in a case where thetransistor 95 goes into the on state, the resistance value of theresistor 97 and an on-resistance of the transistor 95 constitute anoutput impedance of the sub-driver 490. The same applies to thesub-driver 491. Configuring the driver 49A in this way makes it possibleto reduce the number of elements, and as a result, it is possible toreduce a circuit area.

FIG. 31 illustrates a configuration example of another driver 59Aaccording to the present modification example. This driver 59Acorresponds to the driver 29A according to the above-describedembodiment. The driver 59A includes two sub-drivers 590 and 591. Thesub-driver 590 includes M circuits CC0 (circuits CC0 ₁ to CC0 _(M)). Thesub-driver 491 includes N circuits CC1 (circuits CC1 ₁ to CC1 _(N)). Thecircuits CC0 ₁ to CC0 _(M) and CC1 ₁ to CC1 _(N) each include thetransistors 91, 94, and 95 and a resistor 98.

First, the circuits CC0 ₁ to CC0 _(M) are described. In each of thecircuits CC0 ₁ to CC0 _(M), the gate of the transistor 91 is suppliedwith the signal UPA0, and the drain is supplied with the voltage V1, andthe source is coupled to the drains of the transistors 94 and 95 and oneend of the resistor 98. The gate of the transistor 94 is supplied withthe signal DNA0, and the drain is coupled to the source of thetransistor 91, the drain of the transistor 95, and the one end of theresistor 98, and the source is grounded. The gate of the transistor 95is supplied with the signal MDA0, and the source is supplied with thevoltage Vdc generated by the voltage generator 50, and the drain iscoupled to the source of the transistor 91, the drain of the transistor94, and the one end of the resistor 98. The one end of the resistor 98is coupled to the source of the transistor 91 and the drains of thetransistors 94 and 95, and the other end is coupled to the outputterminal ToutA.

Next, the circuits CC1 ₁ to CC1 _(N) are described. In each of thecircuits CC1 ₁ to CC1 _(N), the gate of the transistor 91 is suppliedwith the signal UPA1. The gate of the transistor 94 is supplied with thesignal DNA1. The gate of the transistor 95 is supplied with the signalMDA1. Except for these, the circuits CC1 ₁ to CC1 _(N) are similar tothe circuits CC0 ₁ to CC0 _(M).

In this driver 59A, the resistor 98 corresponds to the resistors 92, 93,and 96 in the driver 29A (FIG. 8) according to the above-describedembodiment. That is, for example, in the sub-driver 590, in a case wherethe transistor 91 goes into the on state, a resistance value of theresistor 98 and an on-resistance of the transistor 91 constitute anoutput impedance of the sub-driver 590; in a case where the transistor94 goes into the on state, the resistance value of the resistor 98 andan on-resistance of the transistor 94 constitute an output impedance ofthe sub-driver 590; and in a case where the transistor 95 goes into theon state, the resistance value of the resistor 98 and an on-resistanceof the transistor 95 constitute an output impedance of the sub-driver590. The same applies to the sub-driver 591. Configuring the driver 59Ain this way makes it possible to reduce the number of elements, and as aresult, it is possible to reduce an circuit area.

Modification Example 2

In the above-described embodiment, the output unit 26 generates thesignals SIGA, SIGB, and SIGC on the basis of the symbol signals Tx1,Tx2, and Tx3, the symbol signals Dtx1, Dtx2, and Dtx3, and the clocksignal TxCK; however, the output unit 26 is not limited thereto. Atransmitting device 10A according to the present modification example isdescribed in detail below.

FIG. 32 illustrates a configuration example of a transmitter 20A of thetransmitting device 10A. The transmitter 20A includes a transmittingsymbol generator 22A and an output unit 26A. The transmitting symbolgenerator 22A generates the symbol signals Tx1, Tx2, and Tx3 on thebasis of the transition signals TxF9, TxR9, and TxP9 and the clocksignal TxCK. The output unit 26A generates the signals SIGA, SIGB, andSIGC on the basis of the symbol signals Tx1, Tx2, and Tx3 and the clocksignal TxCK.

FIG. 33 illustrates a configuration example of the output unit 26A. Theoutput unit 26A includes the driver controller 27N and flip-flops 17A,17B and 17C. The driver controller 27N generates the signals MAINAN,SUBAN, MAINBN, SUBBN, MAINCN, and SUBCN on the basis of the symbolsignals Tx1, Tx2, and Tx3 related to the current symbol NS and the clocksignal TxCK. The flip-flop 17A delays the signals MAINAN and SUBAN byone clock of the clock signal TxCK, and outputs the delayed signals assignals MAINAD and SUBAD. The flip-flop 17B delays the signals MAINBNand SUBBN by one clock of the clock signal TxCK, and outputs the delayedsignals as signal MAINBD and SUBBD. The flip-flop 17C delays the signalsMAINCN and SUBCN by one clock of the clock signal TxCK, and outputs thedelayed signals as signal MAINCD and SUBCD.

This configuration also makes it possible to achieve similar effects tothe case of the above-described embodiment.

Modification Example 3

In the above-described embodiment, the transmitting device 10 performs ade-emphasis operation; however, the transmitting device 10 is notlimited thereto, and may perform a pre-emphasis operation. FIG. 34illustrates three voltage states SH, SM, and SL. The voltage state SH isa state corresponding to three high-level voltages VH (VH0, VH1, andVH2); the voltage state SM is a state corresponding to threemedium-level voltages VM (VM0, VM1plus, and VM1minus); and the voltagestate SL is a state corresponding to three low-level voltages VL (VL0,VL1, and VL2). The high-level voltage VH0 is a high-level voltage in acase where pre-emphasis is not applied; the medium-level voltage VM0 isa medium-level voltage in a case where pre-emphasis is not applied; andthe low-level voltage VL0 is a low-level voltage in a case wherepre-emphasis is not applied. This configuration also makes it possibleto achieve similar effects to the case of the above-describedembodiment.

Other Modification Example

Furthermore, two or more of these modification examples may be combined.

2. Application Example

Subsequently, an application example and practical application examplesof the communication system described in the above-described embodimentand modification examples are described.

Application Example

FIG. 35 illustrates an appearance of a smartphone 300 (a multi-functionmobile phone) to which the communication system according to any of theabove-described embodiment, etc. is applied. This smartphone 300 isequipped with various devices. The communication system according to anyof the foregoing embodiments, etc. is applied to a communication systemthat exchanges data between these devices.

FIG. 36 illustrates a configuration example of an application processor310 used in the smartphone 300. The application processor 310 includes aCPU (Central Processing Unit) 311, a memory controller 312, a powersource controller 313, an external interface 314, a GPU (GraphicsProcessing Unit) 315, a media processor 316, a display controller 317,and a MIPI (Mobile Industry Processor Interface) interface 318. In thisexample, the CPU 311, the memory controller 312, the power sourcecontroller 313, the external interface 314, the GPU 315, the mediaprocessor 316, and the display controller 317 are coupled to a systembus 319 to allow for mutual data exchange through the system bus 319.

The CPU 311 processes various information handled by the smartphone 300in accordance with a program. The memory controller 312 controls amemory 501 that the CPU 311 uses in a case where the CPU 311 performsinformation processing. The power source controller 313 controls a powersource of the smartphone 300.

The external interface 314 is an interface for communication with anexternal device, and, in this example, is coupled to a wirelesscommunication section 502 and an image sensor 410. The wirelesscommunication section 502 performs wireless communication with mobilephone base stations, and includes, for example, a baseband unit, RF(Radio Frequency) front-end unit, etc. The image sensor 410 acquires animage, and includes, for example, a CMOS sensor.

The GPU 315 performs image processing. The media processor 316 processesinformation such as voice, text, graphics, etc. The display controller317 controls a display 504 through the MIPI interface 318. The MIPIinterface 318 transmits an image signal to the display 504. For example,a YUV or RGB signal or the like may be used as the image signal. TheMIPI interface 318 operates on the basis of a reference clock suppliedfrom an oscillation circuit 330 including, for example, a crystalresonator. For example, the communication system according to any of theabove-described embodiment, etc. is applied to a communication systembetween the MIPI interface 318 and the display 504.

FIG. 37 illustrates a configuration example of the image sensor 410. Theimage sensor 410 includes a sensor section 411, an ISP (Image SignalProcessor) 412, a JPEG (Joint Photographic Experts Group) encoder 413, aCPU 414, a RAM (Random Access Memory) 415, a ROM (Read-Only Memory) 416,a power source controller 417, an I²C (Inter-Integrated Circuit)interface 418, and a MIPI interface 419. In this example, these blocksare coupled to a system bus 420 to allow for mutual data exchangethrough the system bus 420.

The sensor section 411 acquires an image, and includes, for example, aCMOS sensor. The ISP 412 performs a predetermined process on the imageacquired by the sensor section 411. The JPEG encoder 413 generates aJPEG image through encoding the image processed by the ISP 412. The CPU414 controls the respective blocks of the image sensor 410 in accordancewith a program. The RAM 415 is a memory that the CPU 414 uses in a casewhere the CPU 414 performs information processing. The ROM 416 storesthe program executed by the CPU 414, a setting value obtained throughcalibration, etc. The power source controller 417 controls a powersource of the image sensor 410. The I²C interface 418 receives a controlsignal from the application processor 310. Furthermore, although notillustrated, the image sensor 410 receives a clock signal as well as thecontrol signal from the application processor 310. Specifically, theimage sensor 410 is configured to be able to operate on the basis ofclock signals of various frequencies. The MIPI interface 419 transmitsan image signal to the application processor 310. For example, a YUV orRGB signal or the like may be used as the image signal. The MIPIinterface 419 operates on the basis of a reference clock supplied froman oscillation circuit 430 including, for example, a crystal resonator.For example, the communication system according to any of theabove-described embodiment, etc. is applied to a communication systembetween the MIPI interface 419 and the application processor 310.

The technology according to the present disclosure is applicable tovarious products. For example, the technology according to the presentdisclosure may be achieved in the form of an apparatus to be mounted toa mobile body of any kind. Examples of the mobile body include anautomobile, an electric vehicle, a hybrid electric vehicle, amotorcycle, a bicycle, a personal mobility, an airplane, an unmannedaerial vehicle, a vessel, a robot, a construction machine, anagricultural machine (a tractor), etc.

Practical Application Example 1

FIG. 38 is a block diagram depicting an example of schematicconfiguration of a vehicle control system 7000 as an example of a mobilebody control system to which the technology according to an embodimentof the present disclosure can be applied. The vehicle control system7000 includes a plurality of electronic control units connected to eachother via a communication network 7010. In the example depicted in FIG.38, the vehicle control system 7000 includes a driving system controlunit 7100, a body system control unit 7200, a battery control unit 7300,an outside-vehicle information detecting unit 7400, an in-vehicleinformation detecting unit 7500, and an integrated control unit 7600.The communication network 7010 connecting the plurality of control unitsto each other may, for example, be a vehicle-mounted communicationnetwork compliant with an arbitrary standard such as controller areanetwork (CAN), local interconnect network (LIN), local area network(LAN), FlexRay, or the like.

Each of the control units includes: a microcomputer that performsarithmetic processing according to various kinds of programs; a storagesection that stores the programs executed by the microcomputer,parameters used for various kinds of operations, or the like; and adriving circuit that drives various kinds of control target devices.Each of the control units further includes: a network interface (I/F)for performing communication with other control units via thecommunication network 7010; and a communication I/F for performingcommunication with a device, a sensor, or the like within and withoutthe vehicle by wire communication or radio communication. A functionalconfiguration of the integrated control unit 7600 illustrated in FIG. 38includes a microcomputer 7610, a general-purpose communication I/F 7620,a dedicated communication I/F 7630, a positioning section 7640, a beaconreceiving section 7650, an in-vehicle device I/F 7660, a sound/imageoutput section 7670, a vehicle-mounted network I/F 7680, and a storagesection 7690. The other control units similarly include a microcomputer,a communication I/F, a storage section, and the like.

The driving system control unit 7100 controls the operation of devicesrelated to the driving system of the vehicle in accordance with variouskinds of programs. For example, the driving system control unit 7100functions as a control device for a driving force generating device forgenerating the driving force of the vehicle, such as an internalcombustion engine, a driving motor, or the like, a driving forcetransmitting mechanism for transmitting the driving force to wheels, asteering mechanism for adjusting the steering angle of the vehicle, abraking device for generating the braking force of the vehicle, and thelike. The driving system control unit 7100 may have a function as acontrol device of an antilock brake system (ABS), electronic stabilitycontrol (ESC), or the like.

The driving system control unit 7100 is connected with a vehicle statedetecting section 7110. The vehicle state detecting section 7110, forexample, includes at least one of a gyro sensor that detects the angularvelocity of axial rotational movement of a vehicle body, an accelerationsensor that detects the acceleration of the vehicle, and sensors fordetecting an amount of operation of an accelerator pedal, an amount ofoperation of a brake pedal, the steering angle of a steering wheel, anengine speed or the rotational speed of wheels, and the like. Thedriving system control unit 7100 performs arithmetic processing using asignal input from the vehicle state detecting section 7110, and controlsthe internal combustion engine, the driving motor, an electric powersteering device, the brake device, and the like.

The body system control unit 7200 controls the operation of variouskinds of devices provided to the vehicle body in accordance with variouskinds of programs. For example, the body system control unit 7200functions as a control device for a keyless entry system, a smart keysystem, a power window device, or various kinds of lamps such as aheadlamp, a backup lamp, a brake lamp, a turn signal, a fog lamp, or thelike. In this case, radio waves transmitted from a mobile device as analternative to a key or signals of various kinds of switches can beinput to the body system control unit 7200. The body system control unit7200 receives these input radio waves or signals, and controls a doorlock device, the power window device, the lamps, or the like of thevehicle.

The battery control unit 7300 controls a secondary battery 7310, whichis a power supply source for the driving motor, in accordance withvarious kinds of programs. For example, the battery control unit 7300 issupplied with information about a battery temperature, a battery outputvoltage, an amount of charge remaining in the battery, or the like froma battery device including the secondary battery 7310. The batterycontrol unit 7300 performs arithmetic processing using these signals,and performs control for regulating the temperature of the secondarybattery 7310 or controls a cooling device provided to the battery deviceor the like.

The outside-vehicle information detecting unit 7400 detects informationabout the outside of the vehicle including the vehicle control system7000. For example, the outside-vehicle information detecting unit 7400is connected with at least one of an imaging section 7410 and anoutside-vehicle information detecting section 7420. The imaging section7410 includes at least one of a time-of-flight (ToF) camera, a stereocamera, a monocular camera, an infrared camera, and other cameras. Theoutside-vehicle information detecting section 7420, for example,includes at least one of an environmental sensor for detecting currentatmospheric conditions or weather conditions and a peripheralinformation detecting sensor for detecting another vehicle, an obstacle,a pedestrian, or the like on the periphery of the vehicle including thevehicle control system 7000.

The environmental sensor, for example, may be at least one of a raindrop sensor detecting rain, a fog sensor detecting a fog, a sunshinesensor detecting a degree of sunshine, and a snow sensor detecting asnowfall. The peripheral information detecting sensor may be at leastone of an ultrasonic sensor, a radar device, and a LIDAR device (Lightdetection and Ranging device, or Laser imaging detection and rangingdevice). Each of the imaging section 7410 and the outside-vehicleinformation detecting section 7420 may be provided as an independentsensor or device, or may be provided as a device in which a plurality ofsensors or devices are integrated.

FIG. 39 depicts an example of installation positions of the imagingsection 7410 and the outside-vehicle information detecting section 7420.Imaging sections 7910, 7912, 7914, 7916, and 7918 are, for example,disposed at at least one of positions on a front nose, sideview mirrors,a rear bumper, and a back door of the vehicle 7900 and a position on anupper portion of a windshield within the interior of the vehicle. Theimaging section 7910 provided to the front nose and the imaging section7918 provided to the upper portion of the windshield within the interiorof the vehicle obtain mainly an image of the front of the vehicle 7900.The imaging sections 7912 and 7914 provided to the sideview mirrorsobtain mainly an image of the sides of the vehicle 7900. The imagingsection 7916 provided to the rear bumper or the back door obtains mainlyan image of the rear of the vehicle 7900. The imaging section 7918provided to the upper portion of the windshield within the interior ofthe vehicle is used mainly to detect a preceding vehicle, a pedestrian,an obstacle, a signal, a traffic sign, a lane, or the like.

Incidentally, FIG. 39 depicts an example of photographing ranges of therespective imaging sections 7910, 7912, 7914, and 7916. An imaging rangea represents the imaging range of the imaging section 7910 provided tothe front nose. Imaging ranges b and c respectively represent theimaging ranges of the imaging sections 7912 and 7914 provided to thesideview mirrors. An imaging range d represents the imaging range of theimaging section 7916 provided to the rear bumper or the back door. Abird's-eye image of the vehicle 7900 as viewed from above can beobtained by superimposing image data imaged by the imaging sections7910, 7912, 7914, and 7916, for example.

Outside-vehicle information detecting sections 7920, 7922, 7924, 7926,7928, and 7930 provided to the front, rear, sides, and corners of thevehicle 7900 and the upper portion of the windshield within the interiorof the vehicle may be, for example, an ultrasonic sensor or a radardevice. The outside-vehicle information detecting sections 7920, 7926,and 7930 provided to the front nose of the vehicle 7900, the rearbumper, the back door of the vehicle 7900, and the upper portion of thewindshield within the interior of the vehicle may be a LIDAR device, forexample. These outside-vehicle information detecting sections 7920 to7930 are used mainly to detect a preceding vehicle, a pedestrian, anobstacle, or the like.

Returning to FIG. 38, the description will be continued. Theoutside-vehicle information detecting unit 7400 makes the imagingsection 7410 image an image of the outside of the vehicle, and receivesimaged image data. In addition, the outside-vehicle informationdetecting unit 7400 receives detection information from theoutside-vehicle information detecting section 7420 connected to theoutside-vehicle information detecting unit 7400. In a case where theoutside-vehicle information detecting section 7420 is an ultrasonicsensor, a radar device, or a LIDAR device, the outside-vehicleinformation detecting unit 7400 transmits an ultrasonic wave, anelectromagnetic wave, or the like, and receives information of areceived reflected wave. On the basis of the received information, theoutside-vehicle information detecting unit 7400 may perform processingof detecting an object such as a human, a vehicle, an obstacle, a sign,a character on a road surface, or the like, or processing of detecting adistance thereto. The outside-vehicle information detecting unit 7400may perform environment recognition processing of recognizing arainfall, a fog, road surface conditions, or the like on the basis ofthe received information. The outside-vehicle information detecting unit7400 may calculate a distance to an object outside the vehicle on thebasis of the received information.

In addition, on the basis of the received image data, theoutside-vehicle information detecting unit 7400 may perform imagerecognition processing of recognizing a human, a vehicle, an obstacle, asign, a character on a road surface, or the like, or processing ofdetecting a distance thereto. The outside-vehicle information detectingunit 7400 may subject the received image data to processing such asdistortion correction, alignment, or the like, and combine the imagedata imaged by a plurality of different imaging sections 7410 togenerate a bird's-eye image or a panoramic image. The outside-vehicleinformation detecting unit 7400 may perform viewpoint conversionprocessing using the image data imaged by the imaging section 7410including the different imaging parts.

The in-vehicle information detecting unit 7500 detects information aboutthe inside of the vehicle. The in-vehicle information detecting unit7500 is, for example, connected with a driver state detecting section7510 that detects the state of a driver. The driver state detectingsection 7510 may include a camera that images the driver, a biosensorthat detects biological information of the driver, a microphone thatcollects sound within the interior of the vehicle, or the like. Thebiosensor is, for example, disposed in a seat surface, the steeringwheel, or the like, and detects biological information of an occupantsitting in a seat or the driver holding the steering wheel. On the basisof detection information input from the driver state detecting section7510, the in-vehicle information detecting unit 7500 may calculate adegree of fatigue of the driver or a degree of concentration of thedriver, or may determine whether the driver is dozing. The in-vehicleinformation detecting unit 7500 may subject an audio signal obtained bythe collection of the sound to processing such as noise cancelingprocessing or the like.

The integrated control unit 7600 controls general operation within thevehicle control system 7000 in accordance with various kinds ofprograms. The integrated control unit 7600 is connected with an inputsection 7800. The input section 7800 is implemented by a device capableof input operation by an occupant, such, for example, as a touch panel,a button, a microphone, a switch, a lever, or the like. The integratedcontrol unit 7600 may be supplied with data obtained by voicerecognition of voice input through the microphone. The input section7800 may, for example, be a remote control device using infrared rays orother radio waves, or an external connecting device such as a mobiletelephone, a personal digital assistant (PDA), or the like that supportsoperation of the vehicle control system 7000. The input section 7800 maybe, for example, a camera. In that case, an occupant can inputinformation by gesture. Alternatively, data may be input which isobtained by detecting the movement of a wearable device that an occupantwears. Further, the input section 7800 may, for example, include aninput control circuit or the like that generates an input signal on thebasis of information input by an occupant or the like using theabove-described input section 7800, and which outputs the generatedinput signal to the integrated control unit 7600. An occupant or thelike inputs various kinds of data or gives an instruction for processingoperation to the vehicle control system 7000 by operating the inputsection 7800.

The storage section 7690 may include a read only memory (ROM) thatstores various kinds of programs executed by the microcomputer and arandom access memory (RAM) that stores various kinds of parameters,operation results, sensor values, or the like. In addition, the storagesection 7690 may be implemented by a magnetic storage device such as ahard disc drive (HDD) or the like, a semiconductor storage device, anoptical storage device, a magneto-optical storage device, or the like.

The general-purpose communication I/F 7620 is a communication I/F usedwidely, which communication I/F mediates communication with variousapparatuses present in an external environment 7750. The general-purposecommunication I/F 7620 may implement a cellular communication protocolsuch as global system for mobile communications (GSM), worldwideinteroperability for microwave access (WiMAX), long term evolution(LTE)), LTE-advanced (LTE-A), or the like, or another wirelesscommunication protocol such as wireless LAN (referred to also aswireless fidelity (Wi-Fi), Bluetooth, or the like. The general-purposecommunication I/F 7620 may, for example, connect to an apparatus (forexample, an application server or a control server) present on anexternal network (for example, the Internet, a cloud network, or acompany-specific network) via a base station or an access point. Inaddition, the general-purpose communication I/F 7620 may connect to aterminal present in the vicinity of the vehicle (which terminal is, forexample, a terminal of the driver, a pedestrian, or a store, or amachine type communication (MTC) terminal) using a peer to peer (P2P)technology, for example.

The dedicated communication I/F 7630 is a communication I/F thatsupports a communication protocol developed for use in vehicles. Thededicated communication I/F 7630 may implement a standard protocol such,for example, as wireless access in vehicle environment (WAVE), which isa combination of institute of electrical and electronic engineers (IEEE)802.11p as a lower layer and IEEE 1609 as a higher layer, dedicatedshort range communications (DSRC), or a cellular communication protocol.The dedicated communication I/F 7630 typically carries out V2Xcommunication as a concept including one or more of communicationbetween a vehicle and a vehicle (Vehicle to Vehicle), communicationbetween a road and a vehicle (Vehicle to Infrastructure), communicationbetween a vehicle and a home (Vehicle to Home), and communicationbetween a pedestrian and a vehicle (Vehicle to Pedestrian).

The positioning section 7640, for example, performs positioning byreceiving a global navigation satellite system (GNSS) signal from a GNSSsatellite (for example, a GPS signal from a global positioning system(GPS) satellite), and generates positional information including thelatitude, longitude, and altitude of the vehicle. Incidentally, thepositioning section 7640 may identify a current position by exchangingsignals with a wireless access point, or may obtain the positionalinformation from a terminal such as a mobile telephone, a personalhandyphone system (PHS), or a smart phone that has a positioningfunction.

The beacon receiving section 7650, for example, receives a radio wave oran electromagnetic wave transmitted from a radio station installed on aroad or the like, and thereby obtains information about the currentposition, congestion, a closed road, a necessary time, or the like.Incidentally, the function of the beacon receiving section 7650 may beincluded in the dedicated communication I/F 7630 described above.

The in-vehicle device I/F 7660 is a communication interface thatmediates connection between the microcomputer 7610 and variousin-vehicle devices 7760 present within the vehicle. The in-vehicledevice I/F 7660 may establish wireless connection using a wirelesscommunication protocol such as wireless LAN, Bluetooth, near fieldcommunication (NFC), or wireless universal serial bus (WUSB). Inaddition, the in-vehicle device I/F 7660 may establish wired connectionby universal serial bus (USB), high-definition multimedia interface(HDMI), mobile high-definition link (MHL), or the like via a connectionterminal (and a cable if necessary) not depicted in the figures. Thein-vehicle devices 7760 may, for example, include at least one of amobile device and a wearable device possessed by an occupant and aninformation device carried into or attached to the vehicle. Thein-vehicle devices 7760 may also include a navigation device thatsearches for a path to an arbitrary destination. The in-vehicle deviceI/F 7660 exchanges control signals or data signals with these in-vehicledevices 7760.

The vehicle-mounted network I/F 7680 is an interface that mediatescommunication between the microcomputer 7610 and the communicationnetwork 7010. The vehicle-mounted network I/F 7680 transmits andreceives signals or the like in conformity with a predetermined protocolsupported by the communication network 7010.

The microcomputer 7610 of the integrated control unit 7600 controls thevehicle control system 7000 in accordance with various kinds of programson the basis of information obtained via at least one of thegeneral-purpose communication I/F 7620, the dedicated communication I/F7630, the positioning section 7640, the beacon receiving section 7650,the in-vehicle device I/F 7660, and the vehicle-mounted network I/F7680. For example, the microcomputer 7610 may calculate a control targetvalue for the driving force generating device, the steering mechanism,or the braking device on the basis of the obtained information about theinside and outside of the vehicle, and output a control command to thedriving system control unit 7100. For example, the microcomputer 7610may perform cooperative control intended to implement functions of anadvanced driver assistance system (ADAS) which functions includecollision avoidance or shock mitigation for the vehicle, followingdriving based on a following distance, vehicle speed maintainingdriving, a warning of collision of the vehicle, a warning of deviationof the vehicle from a lane, or the like. In addition, the microcomputer7610 may perform cooperative control intended for automatic driving,which makes the vehicle to travel autonomously without depending on theoperation of the driver, or the like, by controlling the driving forcegenerating device, the steering mechanism, the braking device, or thelike on the basis of the obtained information about the surroundings ofthe vehicle.

The microcomputer 7610 may generate three-dimensional distanceinformation between the vehicle and an object such as a surroundingstructure, a person, or the like, and generate local map informationincluding information about the surroundings of the current position ofthe vehicle, on the basis of information obtained via at least one ofthe general-purpose communication I/F 7620, the dedicated communicationI/F 7630, the positioning section 7640, the beacon receiving section7650, the in-vehicle device I/F 7660, and the vehicle-mounted networkI/F 7680. In addition, the microcomputer 7610 may predict danger such ascollision of the vehicle, approaching of a pedestrian or the like, anentry to a closed road, or the like on the basis of the obtainedinformation, and generate a warning signal. The warning signal may, forexample, be a signal for producing a warning sound or lighting a warninglamp.

The sound/image output section 7670 transmits an output signal of atleast one of a sound and an image to an output device capable ofvisually or auditorily notifying information to an occupant of thevehicle or the outside of the vehicle. In the example of FIG. 38, anaudio speaker 7710, a display section 7720, and an instrument panel 7730are illustrated as the output device. The display section 7720 may, forexample, include at least one of an on-board display and a head-updisplay. The display section 7720 may have an augmented reality (AR)display function. The output device may be other than these devices, andmay be another device such as headphones, a wearable device such as aneyeglass type display worn by an occupant or the like, a projector, alamp, or the like. In a case where the output device is a displaydevice, the display device visually displays results obtained by variouskinds of processing performed by the microcomputer 7610 or informationreceived from another control unit in various forms such as text, animage, a table, a graph, or the like. In addition, in a case where theoutput device is an audio output device, the audio output deviceconverts an audio signal constituted of reproduced audio data or sounddata or the like into an analog signal, and auditorily outputs theanalog signal.

Incidentally, at least two control units connected to each other via thecommunication network 7010 in the example depicted in FIG. 38 may beintegrated into one control unit. Alternatively, each individual controlunit may include a plurality of control units. Further, the vehiclecontrol system 7000 may include another control unit not depicted in thefigures. In addition, part or the whole of the functions performed byone of the control units in the above description may be assigned toanother control unit. That is, predetermined arithmetic processing maybe performed by any of the control units as long as information istransmitted and received via the communication network 7010. Similarly,a sensor or a device connected to one of the control units may beconnected to another control unit, and a plurality of control units maymutually transmit and receive detection information via thecommunication network 7010.

In the vehicle control system 7000 described above, the communicationsystem 1 according to the present embodiment is applicable to acommunication system between respective blocks in the practicalapplication example illustrated in FIG. 38. Specifically, the presenttechnology is applicable to, for example, a communication system betweenthe imaging section 7410 (the imaging sections 7910, 7912, 7914, 7916,and 7918 and the outside-vehicle information detecting unit 7400.Accordingly, in the vehicle control system 7000, for example, it ispossible to enhance a transmission rate, which makes it possible tosupply an image having high image quality to the outside-vehicleinformation detecting unit 7400. As a result, it is possible for theoutside-vehicle information detecting unit 7400 to more accuratelycomprehend outside-vehicle information.

Practical Application Example 2

The technology according to the present disclosure is applicable tovarious products. For example, the technology according to the presentdisclosure is applicable to an endoscopic surgery system.

FIG. 40 is a view depicting an example of a schematic configuration ofan endoscopic surgery system 5000 to which the technology according toan embodiment of the present disclosure can be applied. In FIG. 40, astate is illustrated in which a surgeon (medical doctor) 5067 is usingthe endoscopic surgery system 5000 to perform surgery for a patient 5071on a patient bed 5069. As depicted, the endoscopic surgery system 5000includes an endoscope 5001, other surgical tools 5017, a supporting armapparatus 5027 which supports the endoscope 5001 thereon, and a cart5037 on which various apparatus for endoscopic surgery are mounted.

In endoscopic surgery, in place of incision of the abdominal wall toperform laparotomy, a plurality of tubular aperture devices calledtrocars 5025 a to 5025 d are used to puncture the abdominal wall. Then,a lens barrel 5003 of the endoscope 5001 and the other surgical tools5017 are inserted into body cavity of the patient 5071 through thetrocars 5025 a to 5025 d. In the example depicted, as the other surgicaltools 5017, a pneumoperitoneum tube 5019, an energy device 5021 andforceps 5023 are inserted into body cavity of the patient 5071. Further,the energy device 5021 is a treatment tool for performing incision andpeeling of a tissue, sealing of a blood vessel or the like by highfrequency current or ultrasonic vibration. However, the surgical tools5017 depicted are mere examples at all, and as the surgical tools 5017,various surgical tools which are generally used in endoscopic surgerysuch as, for example, tweezers or a retractor may be used.

An image of a surgical region in a body cavity of the patient 5071imaged by the endoscope 5001 is displayed on a display apparatus 5041.The surgeon 5067 would use the energy device 5021 or the forceps 5023while watching the image of the surgical region displayed on the displayapparatus 5041 on the real time basis to perform such treatment as, forexample, resection of an affected area. It is to be noted that, thoughnot depicted, the pneumoperitoneum tube 5019, the energy device 5021 andthe forceps 5023 are supported by the surgeon 5067, an assistant or thelike during surgery.

(Supporting Arm Apparatus)

The supporting arm apparatus 5027 includes an arm unit 5031 extendingfrom a base unit 5029. In the example depicted, the arm unit 5031includes joint portions 5033 a, 5033 b and 5033 c and links 5035 a and5035 b and is driven under the control of an arm controlling apparatus5045. The endoscope 5001 is supported by the arm unit 5031 such that theposition and the posture of the endoscope 5001 are controlled.Consequently, stable fixation in position of the endoscope 5001 can beimplemented.

(Endoscope)

The endoscope 5001 includes the lens barrel 5003 which has a region of apredetermined length from a distal end thereof to be inserted into abody cavity of the patient 5071, and a camera head 5005 connected to aproximal end of the lens barrel 5003. In the example depicted, theendoscope 5001 is depicted as a rigid endoscope having the lens barrel5003 of the hard type. However, the endoscope 5001 may otherwise beconfigured as a flexible endoscope having the lens barrel 5003 of theflexible type.

The lens barrel 5003 has, at a distal end thereof, an opening in whichan objective lens is fitted. A light source apparatus 5043 is connectedto the endoscope 5001 such that light generated by the light sourceapparatus 5043 is introduced to a distal end of the lens barrel by alight guide extending in the inside of the lens barrel 5003 and isirradiated toward an observation target in a body cavity of the patient5071 through the objective lens. It is to be noted that the endoscope5001 may be a forward-viewing endoscope or may be an oblique-viewingendoscope or a side-viewing endoscope.

An optical system and an image pickup element are provided in the insideof the camera head 5005 such that reflected light (observation light)from an observation target is condensed on the image pickup element bythe optical system. The observation light is photo-electricallyconverted by the image pickup element to generate an electric signalcorresponding to the observation light, namely, an image signalcorresponding to an observation image. The image signal is transmittedas RAW data to a CCU 5039. It is to be noted that the camera head 5005has a function incorporated therein for suitably driving the opticalsystem of the camera head 5005 to adjust the magnification and the focaldistance.

It is to be noted that, in order to establish compatibility with, forexample, a stereoscopic vision (three dimensional (3D) display), aplurality of image pickup elements may be provided on the camera head5005. In this case, a plurality of relay optical systems are provided inthe inside of the lens barrel 5003 in order to guide observation lightto each of the plurality of image pickup elements.

(Various Apparatus Incorporated in Cart)

The CCU 5039 includes a central processing unit (CPU), a graphicsprocessing unit (GPU) or the like and integrally controls operation ofthe endoscope 5001 and the display apparatus 5041. In particular, theCCU 5039 performs, for an image signal received from the camera head5005, various image processes for displaying an image based on the imagesignal such as, for example, a development process (demosaic process).The CCU 5039 provides the image signal for which the image processeshave been performed to the display apparatus 5041. Further, the CCU 5039transmits a control signal to the camera head 5005 to control driving ofthe camera head 5005. The control signal may include informationrelating to an image pickup condition such as a magnification or a focaldistance.

The display apparatus 5041 displays an image based on an image signalfor which the image processes have been performed by the CCU 5039 underthe control of the CCU 5039. If the endoscope 5001 is ready for imagingof a high resolution such as 4K (horizontal pixel number 3840×verticalpixel number 2160), 8K (horizontal pixel number 7680×vertical pixelnumber 4320) or the like and/or ready for 3D display, then a displayapparatus by which corresponding display of the high resolution and/or3D display are possible may be used as the display apparatus 5041. Wherethe apparatus is ready for imaging of a high resolution such as 4K or8K, if the display apparatus used as the display apparatus 5041 has asize of equal to or not less than 55 inches, then a more immersiveexperience can be obtained. Further, a plurality of display apparatus5041 having different resolutions and/or different sizes may be providedin accordance with purposes.

The light source apparatus 5043 includes a light source such as, forexample, a light emitting diode (LED) and supplies irradiation light forimaging of a surgical region to the endoscope 5001.

The arm controlling apparatus 5045 includes a processor such as, forexample, a CPU and operates in accordance with a predetermined programto control driving of the arm unit 5031 of the supporting arm apparatus5027 in accordance with a predetermined controlling method.

An inputting apparatus 5047 is an input interface for the endoscopicsurgery system 5000. A user can perform inputting of various kinds ofinformation or instruction inputting to the endoscopic surgery system5000 through the inputting apparatus 5047. For example, the user wouldinput various kinds of information relating to surgery such as physicalinformation of a patient, information regarding a surgical procedure ofthe surgery and so forth through the inputting apparatus 5047. Further,the user would input, for example, an instruction to drive the arm unit5031, an instruction to change an image pickup condition (type ofirradiation light, magnification, focal distance or the like) by theendoscope 5001, an instruction to drive the energy device 5021 or thelike through the inputting apparatus 5047.

The type of the inputting apparatus 5047 is not limited and may be thatof any one of various known inputting apparatus. As the inputtingapparatus 5047, for example, a mouse, a keyboard, a touch panel, aswitch, a foot switch 5057 and/or a lever or the like may be applied.Where a touch panel is used as the inputting apparatus 5047, it may beprovided on the display face of the display apparatus 5041.

Otherwise, the inputting apparatus 5047 is a device to be mounted on auser such as, for example, a glasses type wearable device or a headmounted display (HMD), and various kinds of inputting are performed inresponse to a gesture or a line of sight of the user detected by any ofthe devices mentioned. Further, the inputting apparatus 5047 includes acamera which can detect a motion of a user, and various kinds ofinputting are performed in response to a gesture or a line of sight of auser detected from a video imaged by the camera. Further, the inputtingapparatus 5047 includes a microphone which can collect the voice of auser, and various kinds of inputting are performed by voice collected bythe microphone. By configuring the inputting apparatus 5047 such thatvarious kinds of information can be inputted in a contactless fashion inthis manner, especially a user who belongs to a clean area (for example,the surgeon 5067) can operate an apparatus belonging to an unclean areain a contactless fashion. Further, since the user can operate anapparatus without releasing a possessed surgical tool from its hand, theconvenience to the user is improved.

A treatment tool controlling apparatus 5049 controls driving of theenergy device 5021 for cautery or incision of a tissue, sealing of ablood vessel or the like. A pneumoperitoneum apparatus 5051 feeds gasinto a body cavity of the patient 5071 through the pneumoperitoneum tube5019 to inflate the body cavity in order to secure the field of view ofthe endoscope 5001 and secure the working space for the surgeon. Arecorder 5053 is an apparatus capable of recording various kinds ofinformation relating to surgery. A printer 5055 is an apparatus capableof printing various kinds of information relating to surgery in variousforms such as a text, an image or a graph.

In the following, especially a characteristic configuration of theendoscopic surgery system 5000 is described in more detail.

(Supporting Arm Apparatus)

The supporting arm apparatus 5027 includes the base unit 5029 serving asa base, and the arm unit 5031 extending from the base unit 5029. In theexample depicted, the arm unit 5031 includes the plurality of jointportions 5033 a, 5033 b and 5033 c and the plurality of links 5035 a and5035 b connected to each other by the joint portion 5033 b. In FIG. 40,for simplified illustration, the configuration of the arm unit 5031 isdepicted in a simplified form. Actually, the shape, number andarrangement of the joint portions 5033 a to 5033 c and the links 5035 aand 5035 b and the direction and so forth of axes of rotation of thejoint portions 5033 a to 5033 c can be set suitably such that the armunit 5031 has a desired degree of freedom. For example, the arm unit5031 may preferably be configured such that it has a degree of freedomequal to or not less than 6 degrees of freedom. This makes it possibleto move the endoscope 5001 freely within the movable range of the armunit 5031. Consequently, it becomes possible to insert the lens barrel5003 of the endoscope 5001 from a desired direction into a body cavityof the patient 5071.

An actuator is provided in each of the joint portions 5033 a to 5033 c,and the joint portions 5033 a to 5033 c are configured such that theyare rotatable around predetermined axes of rotation thereof by drivingof the respective actuators. The driving of the actuators is controlledby the arm controlling apparatus 5045 to control the rotational angle ofeach of the joint portions 5033 a to 5033 c thereby to control drivingof the arm unit 5031. Consequently, control of the position and theposture of the endoscope 5001 can be implemented. Thereupon, the armcontrolling apparatus 5045 can control driving of the arm unit 5031 byvarious known controlling methods such as force control or positioncontrol.

For example, if the surgeon 5067 suitably performs operation inputtingthrough the inputting apparatus 5047 (including the foot switch 5057),then driving of the arm unit 5031 may be controlled suitably by the armcontrolling apparatus 5045 in response to the operation input to controlthe position and the posture of the endoscope 5001. After the endoscope5001 at the distal end of the arm unit 5031 is moved from an arbitraryposition to a different arbitrary position by the control justdescribed, the endoscope 5001 can be supported fixedly at the positionafter the movement. It is to be noted that the arm unit 5031 may beoperated in a master-slave fashion. In this case, the arm unit 5031 maybe remotely controlled by the user through the inputting apparatus 5047which is placed at a place remote from the operating room.

Further, where force control is applied, the arm controlling apparatus5045 may perform power-assisted control to drive the actuators of thejoint portions 5033 a to 5033 c such that the arm unit 5031 may receiveexternal force by the user and move smoothly following the externalforce. This makes it possible to move, when the user directly toucheswith and moves the arm unit 5031, the arm unit 5031 with comparativelyweak force. Accordingly, it becomes possible for the user to move theendoscope 5001 more intuitively by a simpler and easier operation, andthe convenience to the user can be improved.

Here, generally in endoscopic surgery, the endoscope 5001 is supportedby a medical doctor called scopist. In contrast, where the supportingarm apparatus 5027 is used, the position of the endoscope 5001 can befixed more certainly without hands, and therefore, an image of asurgical region can be obtained stably and surgery can be performedsmoothly.

It is to be noted that the arm controlling apparatus 5045 may notnecessarily be provided on the cart 5037. Further, the arm controllingapparatus 5045 may not necessarily be a single apparatus. For example,the arm controlling apparatus 5045 may be provided in each of the jointportions 5033 a to 5033 c of the arm unit 5031 of the supporting armapparatus 5027 such that the plurality of arm controlling apparatus 5045cooperate with each other to implement driving control of the arm unit5031.

(Light Source Apparatus)

The light source apparatus 5043 supplies irradiation light upon imagingof a surgical region to the endoscope 5001. The light source apparatus5043 includes a white light source which includes, for example, an LED,a laser light source or a combination of them. In this case, where awhite light source includes a combination of red, green, and blue (RGB)laser light sources, since the output intensity and the output timingcan be controlled with a high degree of accuracy for each color (eachwavelength), adjustment of the white balance of a picked up image can beperformed by the light source apparatus 5043. Further, in this case, iflaser beams from the respective RGB laser light sources are irradiatedtime-divisionally on an observation target and driving of the imagepickup elements of the camera head 5005 is controlled in synchronismwith the irradiation timings, then images individually corresponding tothe R, G and B colors can be picked up time-divisionally. According tothe method just described, a color image can be obtained even if a colorfilter is not provided for the image pickup element.

Further, driving of the light source apparatus 5043 may be controlledsuch that the intensity of light to be outputted is changed for eachpredetermined time. By controlling driving of the image pickup elementof the camera head 5005 in synchronism with the timing of the change ofthe intensity of light to acquire images time-divisionally andsynthesizing the images, an image of a high dynamic range free fromunderexposed blocked up shadows and overexposed highlights can becreated.

Further, the light source apparatus 5043 may be configured to supplylight of a predetermined wavelength band ready for special lightobservation. In special light observation, for example, by utilizing thewavelength dependency of absorption of light in a body tissue toirradiate light of a narrower wavelength band in comparison withirradiation light upon ordinary observation (namely, white light),narrow band light observation (narrow band imaging) of imaging apredetermined tissue such as a blood vessel of a superficial portion ofthe mucous membrane or the like in a high contrast is performed.Alternatively, in special light observation, fluorescent observation forobtaining an image from fluorescent light generated by irradiation ofexcitation light may be performed. In fluorescent observation, it ispossible to perform observation of fluorescent light from a body tissueby irradiating excitation light on the body tissue (autofluorescenceobservation) or to obtain a fluorescent light image by locally injectinga reagent such as indocyanine green (ICG) into a body tissue andirradiating excitation light corresponding to a fluorescent lightwavelength of the reagent upon the body tissue. The light sourceapparatus 5043 can be configured to supply such narrow-band light and/orexcitation light suitable for special light observation as describedabove.

(Camera Head and CCU)

Functions of the camera head 5005 of the endoscope 5001 and the CCU 5039are described in more detail with reference to FIG. 41. FIG. 41 is ablock diagram depicting an example of a functional configuration of thecamera head 5005 and the CCU 5039 depicted in FIG. 40.

Referring to FIG. 41, the camera head 5005 has, as functions thereof, alens unit 5007, an image pickup unit 5009, a driving unit 5011, acommunication unit 5013 and a camera head controlling unit 5015.Further, the CCU 5039 has, as functions thereof, a communication unit5059, an image processing unit 5061 and a control unit 5063. The camerahead 5005 and the CCU 5039 are connected to be bidirectionallycommunicable to each other by a transmission cable 5065.

First, a functional configuration of the camera head 5005 is described.The lens unit 5007 is an optical system provided at a connectinglocation of the camera head 5005 to the lens barrel 5003. Observationlight taken in from a distal end of the lens barrel 5003 is introducedinto the camera head 5005 and enters the lens unit 5007. The lens unit5007 includes a combination of a plurality of lenses including a zoomlens and a focusing lens. The lens unit 5007 has optical propertiesadjusted such that the observation light is condensed on a lightreceiving face of the image pickup element of the image pickup unit5009. Further, the zoom lens and the focusing lens are configured suchthat the positions thereof on their optical axis are movable foradjustment of the magnification and the focal point of a picked upimage.

The image pickup unit 5009 includes an image pickup element and disposedat a succeeding stage to the lens unit 5007. Observation light havingpassed through the lens unit 5007 is condensed on the light receivingface of the image pickup element, and an image signal corresponding tothe observation image is generated by photoelectric conversion of theimage pickup element. The image signal generated by the image pickupunit 5009 is provided to the communication unit 5013.

As the image pickup element which is included by the image pickup unit5009, an image sensor, for example, of the complementary metal oxidesemiconductor (CMOS) type is used which has a Bayer array and is capableof picking up an image in color. It is to be noted that, as the imagepickup element, an image pickup element may be used which is ready, forexample, for imaging of an image of a high resolution equal to or notless than 4K. If an image of a surgical region is obtained in a highresolution, then the surgeon 5067 can comprehend a state of the surgicalregion in enhanced details and can proceed with the surgery moresmoothly.

Further, the image pickup element which is included by the image pickupunit 5009 includes such that it has a pair of image pickup elements foracquiring image signals for the right eye and the left eye compatiblewith 3D display. Where 3D display is applied, the surgeon 5067 cancomprehend the depth of a living body tissue in the surgical region moreaccurately. It is to be noted that, if the image pickup unit 5009 isconfigured as that of the multi-plate type, then a plurality of systemsof lens units 5007 are provided corresponding to the individual imagepickup elements of the image pickup unit 5009.

The image pickup unit 5009 may not necessarily be provided on the camerahead 5005. For example, the image pickup unit 5009 may be provided justbehind the objective lens in the inside of the lens barrel 5003.

The driving unit 5011 includes an actuator and moves the zoom lens andthe focusing lens of the lens unit 5007 by a predetermined distancealong the optical axis under the control of the camera head controllingunit 5015. Consequently, the magnification and the focal point of apicked up image by the image pickup unit 5009 can be adjusted suitably.

The communication unit 5013 includes a communication apparatus fortransmitting and receiving various kinds of information to and from theCCU 5039. The communication unit 5013 transmits an image signal acquiredfrom the image pickup unit 5009 as RAW data to the CCU 5039 through thetransmission cable 5065. Thereupon, in order to display a picked upimage of a surgical region in low latency, preferably the image signalis transmitted by optical communication. This is because, upon surgery,the surgeon 5067 performs surgery while observing the state of anaffected area through a picked up image, it is demanded for a movingimage of the surgical region to be displayed on the real time basis asfar as possible in order to achieve surgery with a higher degree ofsafety and certainty. Where optical communication is applied, aphotoelectric conversion module for converting an electric signal intoan optical signal is provided in the communication unit 5013. After theimage signal is converted into an optical signal by the photoelectricconversion module, it is transmitted to the CCU 5039 through thetransmission cable 5065.

Further, the communication unit 5013 receives a control signal forcontrolling driving of the camera head 5005 from the CCU 5039. Thecontrol signal includes information relating to image pickup conditionssuch as, for example, information that a frame rate of a picked up imageis designated, information that an exposure value upon image picking upis designated and/or information that a magnification and a focal pointof a picked up image are designated. The communication unit 5013provides the received control signal to the camera head controlling unit5015. It is to be noted that also the control signal from the CCU 5039may be transmitted by optical communication. In this case, aphotoelectric conversion module for converting an optical signal into anelectric signal is provided in the communication unit 5013. After thecontrol signal is converted into an electric signal by the photoelectricconversion module, it is provided to the camera head controlling unit5015.

It is to be noted that the image pickup conditions such as the framerate, exposure value, magnification or focal point are set automaticallyby the control unit 5063 of the CCU 5039 on the basis of an acquiredimage signal. In other words, an auto exposure (AE) function, an autofocus (AF) function and an auto white balance (AWB) function areincorporated in the endoscope 5001.

The camera head controlling unit 5015 controls driving of the camerahead 5005 on the basis of a control signal from the CCU 5039 receivedthrough the communication unit 5013. For example, the camera headcontrolling unit 5015 controls driving of the image pickup element ofthe image pickup unit 5009 on the basis of information that a frame rateof a picked up image is designated and/or information that an exposurevalue upon image picking up is designated. Further, for example, thecamera head controlling unit 5015 controls the driving unit 5011 tosuitably move the zoom lens and the focus lens of the lens unit 5007 onthe basis of information that a magnification and a focal point of apicked up image are designated. The camera head controlling unit 5015may further include a function for storing information for identifyingthe lens barrel 5003 and/or the camera head 5005.

It is to be noted that, by disposing the components such as the lensunit 5007 and the image pickup unit 5009 in a sealed structure havinghigh airtightness and waterproof, the camera head 5005 can be providedwith resistance to an autoclave sterilization process.

Now, a functional configuration of the CCU 5039 is described. Thecommunication unit 5059 includes a communication apparatus fortransmitting and receiving various kinds of information to and from thecamera head 5005. The communication unit 5059 receives an image signaltransmitted thereto from the camera head 5005 through the transmissioncable 5065. Thereupon, the image signal may be transmitted preferably byoptical communication as described above. In this case, for thecompatibility with optical communication, the communication unit 5059includes a photoelectric conversion module for converting an opticalsignal into an electric signal. The communication unit 5059 provides theimage signal after conversion into an electric signal to the imageprocessing unit 5061.

Further, the communication unit 5059 transmits, to the camera head 5005,a control signal for controlling driving of the camera head 5005. Thecontrol signal may also be transmitted by optical communication.

The image processing unit 5061 performs various image processes for animage signal in the form of RAW data transmitted thereto from the camerahead 5005. The image processes include various known signal processessuch as, for example, a development process, an image quality improvingprocess (a bandwidth enhancement process, a super-resolution process, anoise reduction (NR) process and/or an image stabilization process)and/or an enlargement process (electronic zooming process). Further, theimage processing unit 5061 performs a detection process for an imagesignal in order to perform AE, AF and AWB.

The image processing unit 5061 includes a processor such as a CPU or aGPU, and when the processor operates in accordance with a predeterminedprogram, the image processes and the detection process described abovecan be performed. It is to be noted that, where the image processingunit 5061 includes a plurality of GPUs, the image processing unit 5061suitably divides information relating to an image signal such that imageprocesses are performed in parallel by the plurality of GPUs.

The control unit 5063 performs various kinds of control relating toimage picking up of a surgical region by the endoscope 5001 and displayof the picked up image. For example, the control unit 5063 generates acontrol signal for controlling driving of the camera head 5005.Thereupon, if image pickup conditions are inputted by the user, then thecontrol unit 5063 generates a control signal on the basis of the inputby the user. Alternatively, where the endoscope 5001 has an AE function,an AF function and an AWB function incorporated therein, the controlunit 5063 suitably calculates an optimum exposure value, focal distanceand white balance in response to a result of a detection process by theimage processing unit 5061 and generates a control signal.

Further, the control unit 5063 controls the display apparatus 5041 todisplay an image of a surgical region on the basis of an image signalfor which image processes have been performed by the image processingunit 5061. Thereupon, the control unit 5063 recognizes various objectsin the surgical region image using various image recognitiontechnologies. For example, the control unit 5063 can recognize asurgical tool such as forceps, a particular living body region,bleeding, mist when the energy device 5021 is used and so forth bydetecting the shape, color and so forth of edges of the objects includedin the surgical region image. The control unit 5063 causes, when itcontrols the display unit 5041 to display a surgical region image,various kinds of surgery supporting information to be displayed in anoverlapping manner with an image of the surgical region using a resultof the recognition. Where surgery supporting information is displayed inan overlapping manner and presented to the surgeon 5067, the surgeon5067 can proceed with the surgery more safety and certainty.

The transmission cable 5065 which connects the camera head 5005 and theCCU 5039 to each other is an electric signal cable ready forcommunication of an electric signal, an optical fiber ready for opticalcommunication or a composite cable ready for both of electrical andoptical communication.

Here, while, in the example depicted, communication is performed bywired communication using the transmission cable 5065, the communicationbetween the camera head 5005 and the CCU 5039 may be performed otherwiseby wireless communication. Where the communication between the camerahead 5005 and the CCU 5039 is performed by wireless communication, thereis no necessity to lay the transmission cable 5065 in the operatingroom. Therefore, such a situation that movement of medical staff in theoperating room is disturbed by the transmission cable 5065 can beeliminated.

An example of the endoscopic surgery system 5000 to which the technologyaccording to an embodiment of the present disclosure can be applied hasbeen described above. It is to be noted here that, although theendoscopic surgery system 5000 has been described as an example, thesystem to which the technology according to an embodiment of the presentdisclosure can be applied is not limited to the example. For example,the technology according to an embodiment of the present disclosure maybe applied to a flexible endoscopic system for inspection or amicroscopic surgery system.

The technology according to the present disclosure may be suitablyapplied to a communication system between the camera head 5005 and theCCU 5039 of the configurations described above. Specifically, forexample, the transmitting device 10 according to the present technologyis applicable to the communication unit 5013 of the camera head 5005,and the receiving device 30 is applicable to the communication unit 5059of the CCU 5039. Accordingly, in the endoscopic surgery system 5000, forexample, it is possible to increase a transmission rate, which makes itpossible to supply an image having high image quality to the CCU 5039.Consequently, the endoscopic surgery system 5000 makes it possible forthe surgeon 5067 to more accurately comprehend the state of the affectedarea.

Although the present technology has been described above with referenceto some embodiments, modification examples, and application examples toelectronic apparatuses, the present technology is not limited thereto,and may be modified in a variety of ways.

For example, in the above-described embodiment, etc., the voltage levelin each voltage state is set on the basis of the current symbol NS andthe previous symbol DS; however, the voltage level is not limitedthereto. Instead of this, the voltage level in each voltage state may beset, for example, on the basis of the current symbol NS, the previoussymbol DS, and a symbol before the previous symbol DS. In this case, thetransmitting device operates like a so-called three-tap FIR filter andperforms a de-emphasis operation. It is to be noted that the voltagelevel is not limited thereto, and the voltage level in each voltagestate may be set on the basis of four or more symbols including thecurrent symbol NS.

Furthermore, for example, in the above-described embodiment, etc., thethree voltage states SH, SM, and SL are used; however, the number ofvoltage states is not limited thereto, and four or more voltage statesmay be used. For example, in a case where five voltage states are used,for example, the sub-drivers 290 and 291 may be each provided with fivetransistors.

It is to be noted that the effects described in this specification aremere examples and non-limiting, and there may be other effects.

It is to be noted that the present technology may have the followingconfigurations.

-   (1)

A transmitting device including:

a voltage generator that generates a predetermined voltage;

a first driver including a first sub-driver and a second sub-driver, thefirst dub-driver that includes a first switch provided on a path from afirst power source to a first output terminal, a second switch providedon a path from a second power source to the first output terminal, and athird switch provided on a path from the voltage generator to the firstoutput terminal, and is allowed to set a voltage state of the firstoutput terminal to any of a predetermined number of voltage states whichare three or more voltage states, and the second sub-driver that isallowed to adjust a voltage in each of the voltage states of the firstoutput terminal; and

a controller that controls an operation of the first driver to performemphasis.

-   (2)

The transmitting device according to (1), in which the second sub-driverincludes a fourth switch provided on a path from the first power sourceto the first output terminal, a fifth switch provided on a path from thesecond power source to the first output terminal, and a sixth switchprovided on a path from the voltage generator to the first outputterminal.

-   (3)

The transmitting device according to (2), in which the predeterminednumber of voltage states include a first voltage state corresponding toa voltage at the first power source, a second voltage statecorresponding to a voltage at the second power source, and a thirdvoltage state that corresponds to the predetermined voltage and isinterposed between the first voltage state and the second voltage state.

-   (4)

The transmitting device according to (3), in which in a case where atransition of the voltage state of the first output terminal is madefrom the first voltage state to a voltage state other than the firstvoltage state, the controller performs control to put the fifth switchof the fourth, fifth, and sixth switches into an on state.

-   (5)

The transmitting device according to (3) or (4), in which in a casewhere a transition of the voltage state of the first output terminal ismade from the third voltage state to a voltage state other than thethird voltage state, the controller performs control to put the sixthswitch of the fourth, fifth, and sixth switches into an on state.

-   (6)

The transmitting device according to any one of (3) to (5), in which ina case where the voltage state of the first output terminal of thedriver unit is maintained in the first voltage state, the controllerperforms control to put the fifth switch of the fourth, fifth, and sixthswitches into an on state.

-   (7)

The transmitting device according to any one of (3) to (6), in which ina case where the voltage state of the first output terminal ismaintained in the third voltage state, the controller performs controlto put the sixth switch of the fourth, fifth, and sixth switches into anon state.

-   (8)

The transmitting device according to any one of (3) to (7), in which

in a case where the voltage state of the first output terminal is set tothe first voltage state, the controller performs control to put thefirst switch of the first switch, the second switch, and the thirdswitch into an on state

in a case where the voltage state of the first output terminal is set tothe second voltage state, the controller performs control to put thesecond switch of the first switch, the second switch, and the thirdswitch into the on state and

in a case where the voltage state of the first output terminal is set tothe third voltage state, the controller performs control to put thethird switch of the first switch, the second switch, and the thirdswitch into the on state.

-   (9)

The transmitting device according to any one of (1) to (8), in which

the first sub-driver includes:

a first resistor having one end coupled to the first power source, andanother end coupled to one end of the first switch, and

a second resistor having one end coupled to the first output terminal,and another end coupled to one end of the second switch and one end ofthe third switch,

another end of the first switch is coupled to the first output terminal,

another end of the second switch is coupled to the second power source,and

another end of the third switch is coupled to the voltage generator.

-   (10)

The transmitting device according to any one of (1) to (9), furtherincluding:

a second driver including a third sub-driver and a fourth sub-driver,the third sub-driver that is allowed to set a voltage state of a secondoutput terminal to any of the predetermined number of voltage states,and the fourth sub-driver that is allowed to adjust a voltage in each ofthe voltage states of the second output terminal; and

a third driver including a fifth sub-driver and a sixth sub-driver, thefifth sub-driver that is allowed to set a voltage state of a thirdoutput terminal to any of the predetermined number of voltage states,and the sixth sub-driver that is allowed to adjust a voltage in each ofthe voltage states of the third output terminal, in which

the controller also controls operations of the second driver and thethird driver to perform the emphasis.

-   (11)

The transmitting device according to (10), in which the voltage statesof the first output terminal, the second output terminal, and the thirdoutput terminal are different from one another.

-   (12)

The transmitting device according to (10) or (11), further including asignal generator, in which

the first driver, the second driver, and the third driver transmit asequence of symbols,

the signal generator generates a first symbol signal indicating a symboland a second symbol signal indicating a symbol before the symbolindicated by the first symbol signal on the basis of a transition signalindicating a symbol transition, and

the controller controls the operations of the first driver, the seconddriver, and the third driver on the basis of the first symbol signal andthe second symbol signal.

-   (13)

The transmitting device according to (10) or (11), further including asignal generator, in which

the first driver, the second driver, and the third driver transmit asequence of symbols,

the signal generator generates a symbol signal indicating a symbol onthe basis of a transition signal indicating a symbol transition, and

the controller controls the operations of the first driver, the seconddriver, and the third driver on the basis of a sequence of symbolsindicated by the symbol signal.

-   (14)

The transmitting device according to any one of (1) to (13), in which anoutput impedance of the first sub-driver is lower than an outputimpedance of the second sub-driver.

-   (15)

The transmitting device according to any one of (1) to (14), in which anoutput impedance of the first sub-driver and an output impedance of thesecond sub-driver are each settable.

-   (16)

The transmitting device according to any one of (1) to (15), in whichthe emphasis is de-emphasis.

-   (17)

The transmitting device according to any one of (1) to (15), in whichthe emphasis is pre-emphasis.

-   (18)

A transmitting device including:

a driver unit that transmits a data signal with use of a predeterminednumber of voltage states which are three or more voltage states, and isallowed to set a voltage in each of the voltage states;

a controller that sets an emphasis voltage in accordance with atransition between the predetermined number of voltage states, therebycausing the driver unit to perform emphasis; and

a voltage generator, in which

the driver unit includes a first switch provided on a path from a firstpower source to an output terminal, a second switch provided on a pathfrom a second power source to the output terminal, and a third switchprovided on a path from the voltage generator to the output terminal.

-   (19)

A transmitting method including:

controlling an operation of a first sub-driver including a first switchprovided on a path from a first power source to a first output terminal,a second switch provided on a path from a second power source to thefirst output terminal, and a third switch provided on a path from avoltage generator to the first output terminal, thereby setting avoltage state of the first output terminal to any of a predeterminednumber of voltage states which are three or more voltage states; and

controlling an operation of a second sub-driver, thereby adjusting avoltage in each of the voltage states of the first output terminal toperform emphasis.

-   (20)

A communication system provided with a transmitting device and areceiving device, the transmitting device including:

a voltage generator that generates a predetermined voltage;

a first driver including a first sub-driver and a second sub-driver, thefirst dub-driver that includes a first switch provided on a path from afirst power source to a first output terminal, a second switch providedon a path from a second power source to the first output terminal, and athird switch provided on a path from the voltage generator to the firstoutput terminal, and is allowed to set a voltage state of the firstoutput terminal to any of a predetermined number of voltage states whichare three or more voltage states, and the second sub-driver that isallowed to adjust a voltage in each of the voltage states of the firstoutput terminal; and

a controller that controls an operation of the first driver to performemphasis.

This application claims the benefit of Japanese Priority PatentApplication JP2016-145899 filed with the Japan Patent Office on Jul. 26,2016, the entire contents of which are incorporated herein by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A transmitting device comprising: a voltagegenerator that generates a predetermined voltage; a first driverincluding a first sub-driver and a second sub-driver, the firstsub-driver including a first switch provided on a path from a firstpower source to a first output terminal, a second switch provided on apath from a second power source to the first output terminal, and athird switch provided on a path from the voltage generator to the firstoutput terminal, and being configured to set a voltage state of thefirst output terminal to any of a predetermined number of voltage stateswhich are three or more voltage states, and the second sub-driver beingconfigured to adjust a voltage in each of the voltage states of thefirst output terminal; and a controller that controls an operation ofthe first driver to perform emphasis, wherein the second sub-driverincludes a fourth switch provided on a path from the first power sourceto the first output terminal, a fifth switch provided on a path from thesecond power source to the first output terminal, and a sixth switchprovided on a path from the voltage generator to the first outputterminal.
 2. The transmitting device according to claim 1, wherein thepredetermined number of voltage states include a first voltage statecorresponding to a voltage at the first power source, a second voltagestate corresponding to a voltage at the second power source, and a thirdvoltage state that corresponds to the predetermined voltage and isinterposed between the first voltage state and the second voltage state.3. The transmitting device according to claim 2, wherein in a case wherea transition of the voltage state of the first output terminal is madefrom the first voltage state to a voltage state other than the firstvoltage state, the controller performs control to put the fifth switchof the fourth, fifth, and sixth switches into an on state.
 4. Thetransmitting device according to claim 2, wherein in a case where atransition of the voltage state of the first output terminal is madefrom the third voltage state to a voltage state other than the thirdvoltage state, the controller performs control to put the sixth switchof the fourth, fifth, and sixth switches into an on state.
 5. Thetransmitting device according to claim 2, wherein in a case where thevoltage state of the first output terminal of the first driver ismaintained in the first voltage state, the controller performs controlto put the fifth switch of the fourth, fifth, and sixth switches into anon state.
 6. The transmitting device according to claim 2, wherein in acase where the voltage state of the first output terminal is maintainedin the third voltage state, the controller performs control to put thesixth switch of the fourth, fifth, and sixth switches into an on state.7. The transmitting device according to claim 2, wherein in a case wherethe voltage state of the first output terminal is set to the firstvoltage state, the controller performs control to put the first switchof the first switch, the second switch, and the third switch into an onstate in a case where the voltage state of the first output terminal isset to the second voltage state, the controller performs control to putthe second switch of the first switch, the second switch, and the thirdswitch into the on state and in a case where the voltage state of thefirst output terminal is set to the third voltage state, the controllerperforms control to put the third switch of the first switch, the secondswitch, and the third switch into the on state.
 8. The transmittingdevice according to claim 1, wherein the first sub-driver includes: afirst resistor having one end coupled to the first power source, andanother end coupled to one end of the first switch, and a secondresistor having one end coupled to the first output terminal, andanother end coupled to one end of the second switch and one end of thethird switch, another end of the first switch is coupled to the firstoutput terminal, another end of the second switch is coupled to thesecond power source, and another end of the third switch is coupled tothe voltage generator.
 9. The transmitting device according to claim 1,further comprising: a second driver including a third sub-driver and afourth sub-driver, the third sub-driver that is allowed to set a voltagestate of a second output terminal to any of the predetermined number ofvoltage states, and the fourth sub-driver that is allowed to adjust avoltage in each of the voltage states of the second output terminal; anda third driver including a fifth sub-driver and a sixth sub-driver, thefifth sub-driver that is allowed to set a voltage state of a thirdoutput terminal to any of the predetermined number of voltage states,and the sixth sub-driver that is allowed to adjust a voltage in each ofthe voltage states of the third output terminal, wherein the controlleralso controls operations of the second driver and the third driver toperform the emphasis.
 10. The transmitting device according to claim 9,wherein the voltage states of the first output terminal, the secondoutput terminal, and the third output terminal are different from oneanother.
 11. The transmitting device according to claim 9, furthercomprising a signal generator, wherein the first driver, the seconddriver, and the third driver transmit a sequence of symbols, the signalgenerator generates a first symbol signal indicating a symbol and asecond symbol signal indicating a symbol before the symbol indicated bythe first symbol signal on a basis of a transition signal indicating asymbol transition, and the controller controls the operations of thefirst driver, the second driver, and the third driver on a basis of thefirst symbol signal and the second symbol signal.
 12. The transmittingdevice according to claim 9, further comprising a signal generator,wherein the first driver, the second driver, and the third drivertransmit a sequence of symbols, the signal generator generates a symbolsignal indicating a symbol on a basis of a transition signal indicatinga symbol transition, and the controller controls the operations of thefirst driver, the second driver, and the third driver on a basis of asequence of symbols indicated by the symbol signal.
 13. The transmittingdevice according to claim 1, wherein an output impedance of the firstsub-driver is lower than an output impedance of the second sub-driver.14. The transmitting device according to claim 1, wherein an outputimpedance of the first sub-driver and an output impedance of the secondsub-driver are each settable.
 15. The transmitting device according toclaim 1, wherein the emphasis is de-emphasis.
 16. The transmittingdevice according to claim 1, wherein the emphasis is pre-emphasis.
 17. Acommunication system provided with a transmitting device and a receivingdevice, the transmitting device comprising: a voltage generator thatgenerates a predetermined voltage; a first driver including a firstsub-driver and a second sub-driver, the first sub-driver including afirst switch provided on a path from a first power source to a firstoutput terminal, a second switch provided on a path from a second powersource to the first output terminal, and a third switch provided on apath from the voltage generator to the first output terminal, and beingconfigured to set a voltage state of the first output terminal to any ofa predetermined number of voltage states which are three or more voltagestates, and the second sub-driver being configured to adjust a voltagein each of the voltage states of the first output terminal; and acontroller that controls an operation of the first driver to performemphasis, wherein the second sub-driver includes a fourth switchprovided on a path from the first power source to the first outputterminal, a fifth switch provided on a path from the second power sourceto the first output terminal, and a sixth switch provided on a path fromthe voltage generator to the first output terminal.
 18. Thecommunication system according to claim 17, wherein the predeterminednumber of voltage states include a first voltage state corresponding toa voltage at the first power source, a second voltage statecorresponding to a voltage at the second power source, and a thirdvoltage state that corresponds to the predetermined voltage and isinterposed between the first voltage state and the second voltage state.19. The communication system according to claim 18, wherein in a casewhere a transition of the voltage state of the first output terminal ismade from the first voltage state to a voltage state other than thefirst voltage state, the controller performs control to put the fifthswitch of the fourth, fifth, and sixth switches into an on state. 20.The communication system according to claim 18, wherein in a case wherea transition of the voltage state of the first output terminal is madefrom the third voltage state to a voltage state other than the thirdvoltage state, the controller performs control to put the sixth switchof the fourth, fifth, and sixth switches into an on state.